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Econ 522 Economics of Law Dan Quint Spring 2017 Lecture 7.

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1 Econ 522 Economics of Law Dan Quint Spring 2017 Lecture 7

2 Monday, we “tested the Coase Theorem”
Can UW undergrads reallocate poker chips efficiently? (Cost me $124 to find out) What happened?

3 actual final allocation fraction of potential gains realized
Our experiment… Take 1: Full Information (values on nametags) starting allocation efficient allocation actual final allocation fraction of potential gains realized 12 red chip purple chip 10 purple chip purple chip 10 purple chip purple chip 8 red chip purple chip red chip 8 purple chip 6 purple chip purple chip 6 4 purple chip 4 purple chip 2 purple chip 32 60 54 22/28 = 79%

4 actual final allocation fraction of potential gains realized
Our experiment… Take 2: Private Information (values hidden) starting allocation efficient allocation actual final allocation fraction of potential gains realized 10 red chip red chip 8 purple chip purple chip 8 purple chip purple chip 6 red chip purple chip 6 purple chip purple chip 4 purple chip purple chip 4 3 purple chip 3 purple chip 2 purple chip 24 48 46 22/24 = 92%

5 Our experiment… Take 3: Uncertainty Take 4: Asymmetric Information
Rolled 3 – chip worth 6 to seller, 9 to buyer Chip traded So we achieved 100% of gains from trade! (Seller accepted less than expected value) Take 4: Asymmetric Information Rolled 5 – worth 10 to seller, 15 to buyer Chip traded (for 11), so we achieved all the gains! (Big leap of faith for buyer to pay 11, but it worked out)

6 Conclusion Coase seems to work pretty well – even when there are potential information problems! Full info: 79% of gains achieved Private info: 92% of gains Uncertainty: 100% Asymmetric info: 100% But that’s in a pretty idealized environment

7 Question to ponder “Recharge shop” owners in India are saving women’s numbers when they add mobile minutes, selling them to harassers What would the Coase Theorem say about efficient “ownership” of knowledge of someone’s phone number? Does Coase apply here? Why/why not? What remedy would make sense here? Source: The Hindustan Times reports the following scam occurring in Uttar Pradesh, the Indian province southwest of Delhi. Many small “recharge shops” exist where people can add minutes to their prepaid mobile phones; some shop owners have begun to save the numbers of girls and women who recharge there, and then sell the numbers to men, who call to harass the women, often with the opening line “I want to make friendship with you”. The phone number of an “ordinary-looking girl” sells for below a dollar, while the phone number of someone “beautiful” sells for about $7.50.

8 what can be privately owned? what can an owner do?
Monday: starting thinking about details of efficient property law system what can be privately owned? what can an owner do? how are property rights established? what remedies are given? We said that any property rights system must address four questions: What things can be privately owned? What can (or can’t) an owner do with his/her property? How are property rights established? And what remedies are given when they are violated? Last time, we addressed the fourth question – remedies – and concluded that: When TC are low, injunctive relief When TC are high, damages

9 Monday: starting thinking about details of efficient property law system
Calabresi/Melamed: three types of remedies Injunctive relief (property rule) – violations prohibited without prior permission, punished severely, but tradable Damages (liability rule) – violations compensated Inalienability – violations punished, not tradable Inalienability… Might make sense when allocation involves large externalities that can’t be overcome Might be a product of governmental paternalism… …or legislator (or voter) repugnance 8 8

10 Monday: starting thinking about details of efficient property law system
When transaction costs are low, use injunctive relief Either rule will lead to efficient allocation (Coase)… …but injunctions are cheaper to implement (court doesn’t have to assess level of harm) When transaction costs are high, use damages If bargaining is impossible, damages  more efficient outcomes (Example: polluter can choose to pollute and pay when that’s more efficient than preventing the damage) Agrees with principle from last week TC low: design law to facilitate trade (normative Coase) TC high: design law to not rely on bargaining (normative Hobbes) 9 9

11 Onward! what can be privately owned? what can an owner do? how are property rights established? what remedies are given?

12 Public versus Private Goods
rivalrous – one’s consumption precludes another excludable – technologically possible to prevent consumption example: apple Public Goods non-rivalrous non-excludable examples defense against nuclear attack infrastructure (roads, bridges) parks, clean air, large fireworks displays You may recall from micro a discussion of Public and Private Goods. Private Goods tend to be characterized by two properties: Rivalrous – one person’s consumption of a private good precludes another person’s enjoyment of its benefits if I eat an apple, you won’t be able to eat that same apple Excludable – it’s technologically possible to prevent others from consuming it It shouldn’t be too hard for me to prevent you from eating it. Public Goods tend to be characterized by the opposite of these two properties: Nonrivalrous – one person’s consumption of a public good does not impact others’ enjoyment of it Nonexcludable – hard to prevent people from taking advantage The cleanest example of a public good is defense against a nuclear attack It’s very hard for me to defend myself from a nuclear attack in a way that doesn’t also protect you a bit and you being safe from nuclear attack doesn’t impact my enjoyment of this privilege. Other public goods are urban infrastructure (bridges and roads) (although roads may become somewhat rivalrous when there is congestion); parks, clean air, the ocean, fireworks displays (like on the homework), and so on.

13 Public versus Private Goods
When private goods are owned publicly, they tend to be overutilized/overexploited A principle you may remember from intermediate micro: When private goods are owned publicly, they tend to be overutilized, or overexploited. This is the point of the Hardin paper, the tragedy of the commons His example: a large common area where everyone is permitted to graze their cattle Since it’s public, nobody considers the cost their herd imposes on the grass So the grass on the commons gets wiped out by overgrazing Same problem as overfishing in the communal lake Or overhunting in unregulated public land Another example of this is congestion on busy roads Most roads are provided publicly (no toll, free to use) When there’s lots of traffic, roads become rivalrous – the more people on the road, the less utility I get from driving on them – so they take on one of the characteristics of a private good But when people are deciding whether or not to drive, they tend not to consider the externality that their choice to drive has on other drivers; so the roads get overused (Some cities are looking at ways to solve this problem with congestion pricing – charging people to use the roads during peak hours, so that people internalize this externality.)

14 Public versus Private Goods
When private goods are owned publicly, they tend to be overutilized/overexploited When public goods are privately owned, they tend to be underprovided/undersupplied One the other hand, when public goods are privately owned, they face the opposite problem: they will be underprovided You just saw an example of this: the fireworks problem on the homework Fireworks are a public good; so if each person decides for himself how much to contribute, we get less than the efficient amount of fireworks Another example of this would be artistic creations if they weren’t protected by intellectual property Certainly, something like a song, or a book, is non-rivalrous And technology has made these things much closer to non-excludable If anyone could freely copy my song, or my book, once it’s written, then I might get very little reward for writing it; so I have little incentive to create, and might choose not to Recall our earlier story of a hops farmer and a brewery When there was a single hops farmer, he could negotiate with the brewery to reduce pollution and breathe cleaner air But if the dirty air affects lots of people, it becomes a “public bad” – and if each person tries to negotiate separately with the brewery to reduce pollution, they will reduce it less than efficiency would suggest.

15 Public versus Private Goods
When private goods are owned publicly, they tend to be overutilized/overexploited When public goods are privately owned, they tend to be underprovided/undersupplied Efficiency suggests private goods should be privately owned, and public goods should be publicly provided/regulated These two observations bring us to the following general rule: Efficiency suggests that private goods should be privately owned, and public goods should be publicly provided or regulated Private ownership of private goods avoids overuse, and allows trade, leading to efficient allocations (Coase) Public provision of public goods avoids undersupply This also gives us another interpretation of the Demsetz example we did last week, of the development of property rights to land among Native Americans What makes the case interesting is that land can be either a public or a private good, depending on the circumstances. National forests can be thought of as a public good they’re a good thing ecologically, they’re pretty to drive by and hike in, I can enjoy them even if other people are enjoying them, and it’s hard to exclude other people from getting their benefits. On the other hand, 900 square feet in the middle of a city is a private good if I build an apartment there and live in it, that precludes you doing the same; and as long as I get a door with a decent lock, I can keep you out. Demsetz’s observation was that property rights over land developed among Native Americans as the fur trade became more important economically We can interpret this in terms of public and private goods.

16 Public versus Private Goods
When private goods are owned publicly, they tend to be overutilized/overexploited When public goods are privately owned, they tend to be underprovided/undersupplied Efficiency suggests private goods should be privately owned, and public goods should be publicly provided/regulated Before the fur trade, land was pretty much a public good There was no shortage of animals, so hunting grounds were not particularly rivalrous – I could hunt on your land, and still leave enough game for you to hunt the next day With the emergence of the fur trade came stronger incentives for hunting Fur-bearing animals became more valuable, so were hunted more, so became scarce, so the land became a rivalrous good – the more I hunted, the less luck you would have hunting on the same land So the emergence of the fur trade led to a sort of transition of land from being a public to a private good Efficiency would then suggest that at the same time, it should go from being publicly owned (everyone could hunt on it) to being privately owned (one family might have exclusive rights to hunt in a particular area) Which is pretty much what happened So the general principle is, private goods should be owned privately, and public goods should be publicly provided/regulated The book mentions the move in the 1990s toward deregulation/privitization as an example of correcting a situation of private goods being publicly supplied services that did not involve externalities, and could therefore be supplied by private industry, but for historical reasons were being run by the government in the 1990s, there was a big movement to dismantle or sell off government monopolies on trains, planes, and other services worldwide.

17 This also accords with the principle from last week
Transaction costs low  facilitate voluntary trade Private goods – low transaction costs Private ownership facilitates trade Transaction costs high  allocate rights efficiently Public goods – high transaction costs Public provision/regulation required to get efficient amount

18 A different view: transaction costs
Clean air Large number of people affected  transaction costs high  injunctive relief unlikely to work well Still two options One: give property owners right to clean air, protected by damages Two: public regulation Argue for one or the other by comparing costs of each Damages: costs are legal cost of lawsuits or pretrial negotiations Regulation: administrative costs, error costs if level is not chosen correctly Cooter and Ulen also point out that in many cases, either type of ownership, public or private, will involve some transaction costs, and the case can be made for one or the other by considering the magnitude of these costs (In fact, we can think of public goods as goods where costs of privately transacting are too high – enforcement costs are high because the good is nonexcludable, or bargaining costs are high because so many people are affected) Consider again the example of clean air If there are lots of consumers affected by pollution from a factory, injunctive relief is unlikely to work well, since transaction costs tend to be high when there are lots of parties affected However, there are still two possible ways to maintain clean air One way is to grant property owners the right to clean air, but protected by damages; so that a factory, if it felt it worthwhile, could choose to pollute and pay damages Alternatively, clean air could be viewed as a public good, and regulated by a government agency We can argue for the efficiency of one system or the other by comparing the magnitude of these transaction costs In the case of damages, the transaction cost here would be the legal cost of these lawsuits, or pretrial negotiations, including the cost to the court of calculating damages In the case of regulation, this would involve the administrative costs of setting up and running a government agency to regulate air quality, and could run the risk of the level of pollution not being the one that is socially optimal Whichever costs would be lower, suggests which system would be more efficient 17 17

19 How do we design an efficient property law system?
what can be privately owned? what can an owner do? how are property rights established? what remedies are given? We’ve addressed two questions so far. What can be privately owned? (In general, private goods should be privately owned, public goods should be publicly provided or regulated.) What remedies should be given? (In general, injunctive relief when transaction costs are low, damages when transaction costs are high)

20 What can an owner do with his/her property?
For efficiency: principle of maximum liberty Owners can do whatever they like with their property… …provided that doesn’t interfere with others’ property or rights That is, you can do anything you like so long as it doesn’t impose an externality (nuisance) on anyone else Textbook: common law often approximates rule of maximum liberty But does it really? What about bans on repugnant markets? And… Next, we consider the question, what can an owner do with his property? Efficiency suggests that anything that makes me better off, and doesn’t affect anyone else, is efficient And so efficiency suggests the principle of maximum liberty maximum liberty suggests that owners can do anything with their property that does not interfere with other peoples’ property or rights that is, you can do anything you like with your property as long as it doesn’t impose an externality on anyone else once one person’s actions begin to affect another, we run into what we’ve already been looking at – nuisance law In the textbook, they make the case that the common law approximates the rule of maximum liberty, although I’m a bit skeptical Legislatures may pass laws that impose further restrictions on what people can do with their property In general, these laws are only efficient if the behavior they are restricting causes an externality.

21 “Maximum liberty” vs. government’s right to regulate
Ruling a few years ago by a Dane County judge Plaintiffs argued they had a “fundamental right to own a cow, and to use their cows in a manner that does not cause harm to a third party” Judge responded: “Plaintiffs do not have a fundamental right to own and use a dairy cow or a dairy herd Plaintiffs do not have a fundamental right to consume the milk from their own cow Plaintiffs do not have a fundamental right to board their cow at the farm of a farmer The private contract does not fall outside the scope of the States’ police power Plaintiffs do not have a fundamental right to produce and consume the foods of their choice DATCP has jurisdiction to regulate the Plaintiffs’ conduct” Here’s an example, though, showing that while “maximum liberty” is a nice theoretical idea, it’s not a legal assumption Plaintiffs owned a couple of cows for their own milk consumption, that they arranged to board at a local farm Asked a judge to clarify that their arrangement was legal In August 2011, he ruled against them They requested a clarification, which he issued that September The ruling is discussed here: The discussion in the blog is rather one-sided. There may be a lot more going on here. Might just be saying, can’t own a dairy farm and also segregate a couple cows for “personal use” that are exempt from usual rules. There are likely legitimate reasons (food safety, animal cruelty) to regulate the dairy industry And there may be good reasons to not draw a line between private ownership of a cow or two and running a dairy business But the strength of the language with which the judge “smacked down” the plaintiff does underline the point that “maximum liberty” is not necessarily an accurate description of the world we actually live in (Also: if the judge were applying a new regulation that had just passed after the plaintiffs already owned their cows, this could constitute a regulatory taking – but in this case, he’s applying preexisting regulations that the plaintiffs hoped wouldn’t apply to “private use” cows)

22 How do we design an efficient property law system?
what can be privately owned? what can an owner do? how are property rights established? what remedies are given? Finally, how are property rights established?

23 Fugitive property Hammonds v. Central Kentucky Natural Gas Co.
Central Kentucky leased land lying above natural gas deposits Geological dome lay partly under Hammonds’ land Central Kentucky drilled down and extracted the gas Hammonds sued, claiming some of the gas was his (Anybody see “There Will Be Blood”?) Hammonds Central KY Fugitive property is property that moves around or has indefinite boundaries – like foxes or whales Another example: natural gas Hammonds v. Central Kentucky Natural Gas Company (1934) The Central Kentucky Natural Gas Company leased tracts of land above deposits of natural gas But the geological dome of natural gas lay partly under the land they were leasing, and partly under someone else’s land When the company began extracting the gas, Hammonds, one of the other landowners, sued, claiming that some of the gas they were extracting came from under her land. Anybody see the movie “There Will Be Blood”? toward the end, Eli returns to town, wants to lease Daniel Day Lewis the last bit of land in town that he hasn’t yet drilled for oil on Daniel Day Lewis points out the land is worthless – the oil moved around, and he was able to extract all of it through other land he had leased (Then he makes a speech about drinking Eli’s milkshake, and then kills him with a bowling pin.)

24 Two principles for establishing ownership
First Possession nobody owns fugitive property until someone possesses it first to “capture” a resource owns it Central Kentucky would own all the gas Tied Ownership ownership of fugitive property tied (linked) to something else – here, ownership of the surface so ownership already determined before resource is extracted Hammonds would own some of the gas, since under his land principle of accession – a new thing is owned by the owner of the proximate or prominent property There are two different principles for how to establish ownership of fugitive property: first possession – fugitive property does not belong to anybody until someone extracts it, establishing ownership tied ownership – ownership of fugitive property is tied to something else which is easier to establish – in this case, the owner of the surface under which the natural gas resides Under first possession, Central Kentucky Natural Gas Company would be entitled to whatever gas it extracted Under tied ownership, they would only be entitled to the gas under their own land, and Hammond’s claim would be valid Tied ownership would also suggest that a landowner has rights to the foxes on his own land. Tied ownership might suggest that if you’re at a baseball game and a foul ball lands on your seat, you have automatic rights to it While first possession suggests that whoever grabs the ball owns it. When tied ownership is used, both the common and civil law often tie ownership using the principle of accession a new thing is owned by the owner of the “proximate or prominent” property, that is, the nearest (or most obvious) thing to link ownership to for example, a newborn calf belongs to the owner of its mother when a river shifts and creates new land, the owner of the river bank owns that new land and the owner of a brand name tends to have the default right to the corresponding Internet address

25 First Possession versus Tied Ownership
simpler to apply – easy to determine who possessed property first incentive to invest too much to early in order to establish ownership example: $100 of gas, two companies drilling fast or slow drilling slowly costs $5, drilling fast costs $25 drill same speed  each gets half the gas, one drills fast  75/25 Firm 2 First possession has the advantage of generally being very simple (and therefore cheap) to apply Determining who first possessed property is usually straightforward However, first possession also has a downside It creates an incentive to invest too much too early, in order to establish ownership of a scarce resource That is, firms might expend too many resources trying to establish first possession of a resource, leading to inefficiency For example, imagine there is an underground natural gas deposit, and two firms lease land above the deposit This would create a race between them, since the gas was a scarce resource that belonged to whoever possessed it first This would lead to both firms to try to extract it inefficiently quickly, using means that are more expensive than necessary Example: two firms drilling for $100 worth of gas; drilling slow costs $5, fast costs $25; if both do same speed, 50/50 split; if one does fast, 75/25. Game is: Like prisoner’s dilemma, (fast, fast) is equilibrium, even though (slow,slow) is more efficient So a first possession rule leads to inefficient investment in “possessory acts” – inefficient behavior designed just to claim a valuable resource first Slow Fast 45, 45 20, 50 Slow Firm 1 50, 20 25, 25 Fast

26 First Possession versus Tied Ownership
simpler to apply – easy to determine who possessed property first incentive to invest too much to early in order to establish ownership Tied Ownership encourages efficient use of the resource but, difficulty of establishing and verifying ownership rights Firm 2 Slow Fast Tied ownership avoids this problem If the ownership of the property to which the rights are tied is already established, tied ownership creates the incentive for efficient use of the resource. If the ownership of the natural gas is not in question, the firm can extract it by the most efficient means possible – there is no need to race to get it first Suppose that due to their rights to the surface, each firm knows that however quickly they extract it, they have rights to have the gas Now there’s no reason not to drill slowly Modify the game, and note the new equilibrium Similarly, if salmon belong to nobody until they’re caught, we expect overfishing; But if salmon are the property of the owners of the stream where they spawn, the owners have no incentive to deplete the salmon by overfishing. However, as we saw in the Hammonds case, tied ownership faces the difficulty of establishing and verifying ownership rights it is impossible to figure out “which” part of the natural gas being extracted was under Central Kentucky’s land and which part was under Hammond’s 45, 45 45, 25 Slow Firm 1 25, 45 25, 25 Fast

27 This brings us to the following tradeoff:
Rules that link ownership to possession have the advantage of being easy to administer, and the disadvantage of providing incentives for uneconomic investment in possessory acts. Rules that allow ownership without possession have the advantage of avoiding preemptive investment and the disadvantage of being costly to administer. This brings us to the following tradeoff: Rules that link ownership to possession have the advantage of being easy to administer and the disadvantage of providing incentives for uneconomic investment in possessory acts. Rules that allow ownership without possession have the advantage of avoiding preemptive investment and the disadvantage of being costly to administer. So the problem with a first-possession rule is it leads to an investment in possessory acts, which do not create any value, just transfer it

28 We’ve already seen two examples of this
“Fast fish/loose fish” and “the guy who kills a fox, owns it” are examples of a first possession rule You can’t own a resource until you physically possess it “Iron holds the whale” and “the guy chasing a fox owns it” are examples of a tied ownership rule You can establish ownership of something before you actually possess it (A harpoon, or chasing a fox, gives you a right to it) More complicated/costly to enforce “if the first seeing, starting, or pursuing such animals… should afford the basis of actions against others for intercepting and killing them, it would prove a fertile source of quarrels and litigation” But avoids incentive to poach someone else’s resource This tradeoff was at work in the fox-hunt case, Pierson v Post Awarding the fox to Pierson, the interloper, links ownership to possession, which is the simpler rule But it gives him an incentive to jump in at the end of the hunt, which is inefficient Awarding the fox to Post, the hunter, allows ownership without possession It avoids the incentive problem, but is more difficult to administer, since there is less of a “bright line” to mark when ownership is established and the claim of ownership is harder to prove Similarly, recall that sperm whales are too fast and strong to hunt with harpoons tied to the ship So if first possession (like fast fish/loose fish) were applied to sperm whales, every time a whale was injured and trailing drogues, you’d have a bunch of ships chasing after it, competing to be the first to secure it – clearly inefficient From decision in Pierson v Post: “If the first seeing, starting, or pursuing such animals… should afford the basis of actions against others for intercepting and killing them, it would prove a fertile source of quarrels and litigation”

29 Another nice historical example: the Homestead Act of 1862
Meant to encourage settlement of the Western U.S. Citizens could acquire 160 acres of land for free, provided head of a family or 21 years old “for the purpose of actual cultivation, and not… for the use or benefit of someone else” had to live on the claim for 6 months and make “suitable” improvements Basically a first possession rule for land – by living on the land, you gained ownership of it Friedman: caused people to spend inefficiently much to gain ownership of the land A nice historical example of this can be traced to the Homestead Act of 1862 The Homestead Act was meant to encourage people to settle the Western part of the U.S. It allowed citizens to acquire up to 160 acres of public land, provided the claimant was the head of a family or 21 year old the claim was “for the purpose of actual cultivation, and not, either directly or indirectly, for the use or benefit of” someone else the claimant had to live on the claim for 6 months and make “suitable” improvements before title was granted These requirements were meant to prevent a mad rush to acquire land and do nothing with it The Homestead Act was effectively a first possession rule – you could claim the land by living on it We just saw that first possession rules lead to uneconomic investment in possessory acts Friedman points out that the Homestead Act caused people to spend inefficiently much in order to claim land that would later become valuable Quoting from Law’s Order (p 120):

30 Friedman on the Homestead Act of 1862
“The year is 1862; the piece of land we are considering is… too far from railroads, feed stores, and other people to be cultivated at a profit. …The efficient rule would be to start farming the land the first year that doing so becomes profitable, say But if you set out to homestead the land in 1890, you will get an unpleasant surprise: someone else is already there. …If you want to get the land you will have to come early. By farming it at a loss for a few years you can acquire the right to farm it thereafter at a profit. “The year is 1862; the piece of land we are considering is beyond the margin of settlement, too far from railroads, feed stores, and other people to be cultivated at a profit. As time passes and settlement expands, that situation changes. The efficient rule would be to start farming the land the first year that doing so becomes profitable, say But if you set out to homestead the land in 1890, you will get an unpleasant surprise; someone else is already there. Homesteading land that is already profitable to farm is an attractive proposition, since you not only make money in the process, you also end up with valuable real estate. When valuable rights are being given away for free, there is no shortage of takers. If you want to get the land you will have to come early. By farming it at a loss for a few years you can acquire the right to farm it thereafter at a profit.

31 Friedman on the Homestead Act of 1862
How early will you have to come? Assume the value of the land in 1890 is going to be $20,000, representing the present value of the profit that can be made by farming it from then on. Further assume that the loss from farming it earlier than that is $1,000 a year. If you try to homestead it in 1880, you again find the land already taken. Someone who homesteads in 1880 pays $10,000 in losses for $20,000 in real estate – not as good as getting it for free, but still an attractive deal. …The land will be claimed about 1870, just early enough so that the losses in the early years balance the later gains. It follows that the effect of the Homestead Act was to wipe out, in costs of premature farming, a large part of the land value of the United States.” How early will you have to come? To make things simple, assume the value of the land in 1890 is going to be $20,000, representing the present value of the profit that can be made by farming it from then on. Further assume that the loss from farming it earlier than that is $1,000 a year. If you try to homestead it in 1880, you again find the land already taken. Someone who homesteads in 1880 pays $10,000 dollars in losses for $20,000 in real estate – not as good as getting it for free, but still an attractive deal. Working through the logic of the argument, we conclude that the land will be claimed about 1870, just early enough so that the losses in the early years balance the later gains. It follows that the effect of the Homestead Act was to wipe out, in costs of premature farming, a large part of the land value of the United States.”

32 So, what does an efficient property law system look like?
What things can be privately owned? Private goods are privately owned, public goods are publicly provided What can owners do with their property? Maximum liberty How are property rights established? (Tradeoff between first possession and tied ownership; more examples to come) What remedies are given? Injunctions when transaction costs are low; damages when transaction costs are high

33 Next up Next up: some applications of property law
But first, one more tool…

34 Sequential Rationality

35 Dynamic games and sequential rationality
Game theory we’ve seen so far: static games “everything happens at once” (nobody observes another player’s move before deciding how to act) Dynamic games one player moves first second player learns what first player did, and then moves

36 Let’s go back to a game we’ve seen – the Battle of the Sexes
Player 2 Ballgame Opera 6, 3 0, 0 Ballgame Player 1 0, 0 3, 6 Opera Now change the game so that player 1 moves first Player 1 goes somewhere Player 2 learns what 1 did, then decides where to go 35 35

37 Dynamic games are typically shown as “game trees”
PLAYER 1 Ballgame Opera PLAYER 2 PLAYER 2 Ballgame Opera Ballgame Opera (6, 3) (0, 0) (0, 0) (3, 6) A strategy is one player’s plan for what to do at each decision point he/she acts at Player 1: “Ballgame” or “Opera” Player 2’s strategy is more complicated – can depend on P1’s choice

38 We can expand the matrix to accommodate Player 2’s additional options
Ballgame, Ballgame Ballgame, Opera Opera, Ballgame Opera, Opera 6, 3 6, 3 0, 0 0, 0 Ballgame Player 1 0, 0 3, 6 0, 0 3, 6 Opera Player 2 has four options “Go to the ballgame no matter what” “Go to the ballgame if P1 went to the ballgame, otherwise opera” “Opera if P1 went to the ballgame, otherwise ballgame” “Opera no matter what” 37 37

39 We can solve this game for equilibrium in the “usual” way
Player 2 Ballgame, Ballgame Ballgame, Opera Opera, Ballgame Opera, Opera 6, 3 6, 3 0, 0 0, 0 Ballgame Player 1 0, 0 3, 6 0, 0 3, 6 Opera Three equilibria: 1 goes to ballgame, 2 plays “ballgame no matter what” 1 goes to ballgame, 2 plays “go wherever 1 went” 1 goes to opera, 2 plays “opera no matter what” Are all of these “reasonable”? 38 38

40 Are all these equilibria “reasonable”?
Consider the equilibrium where player 2 plans to go to the opera no matter what player 1 therefore goes to the opera Player 1 might wonder… “Suppose I changed my mind and went to the ballgame. Once I’m there, player 2 has to choose between sticking to the plan, going to the opera, and getting 0… …versus following me to the ballgame and getting 3. If player 2 is rational and I go to the ballgame, she should follow me there, and I’ll end up with a payoff of 6!”

41 Sequential rationality
Sequential rationality is when a player can count on the other players to behave rationally from that point forward Similar to “dynamic consistency” (macro) When an equilibrium satisfies sequential rationality, we call it a Subgame-Perfect Equilibrium Players play best-responses both in the game as a whole, and in each “subgame,” or part of the game Rules out the opera-opera equilibrium: in the subgame where P1 had already gone to the ballgame, P2 wasn’t playing a best-response In fact, P2 only has one strategy that is sequentially rational: do whatever player 1 did! also called “dynamic consistency” in macro - people make a plan at the beginning, but that plan still seems like the best available option when they reconsider it later, otherwise they wouldn’t stick to it

42 Subgame Perfect Equilibria are found by Backward Induction
PLAYER 1 Ballgame Opera PLAYER 2 PLAYER 2 Ballgame Opera Ballgame Opera (6, 3) (0, 0) (0, 0) (3, 6) Start at the “bottom,” solve for what P2 would do at each point If P2 is rational and P1 knows it, P1 can infer what payoff he would get from each move Now figure out what P1 would do, given those payoffs

43 Subgame Perfect Equilibria are found by Backward Induction
PLAYER 1 Ballgame Opera PLAYER 2 PLAYER 2 Ballgame Opera Ballgame Opera (6, 3) (0, 0) (0, 0) (3, 6) This game has a unique subgame-perfect equilibrium Player 1 plays Ballgame Player 2 plays Ballgame if 1 plays Ballgame, Opera if 1 plays Opera “Most” dynamic games have just one SPE

44 Moving first can be good or bad, depending on the game
Battle of the sexes: moving first is good You know your partner will accommodate whatever you do… …so you get your first choice Some games: being able to “commit” to a decision, while your opponent still has to decide, can be good! (Another example: entry game) Scissors-paper-rock: moving first is terrible You always lose Some games: reacting to your opponent’s move is good!

45 When we look at dynamic games, we’ll always look only at subgame-perfect equilibrium
Key assumption: common knowledge of rationality Player 1 knows player 2 is rational… …so whatever he does, she’ll do what’s best for her… …so player 1 can confidently go to the ballgame This is the key to sequential rationality The assumption that, whatever happens first, players will continue to act rationally in their own best interest Which means we can “solve the game” from the end, and figure out the beginning players’ optimal moves (Backward induction has been used to solve checkers in 2007 – it’s a draw – and will eventually solve chess…) The key assumption here is common knowledge of rationality The players know each others’ payoff functions, everyone is rational, everyone knows everyone is rational, everyone knows everyone knows everyone is rational, and so on If you’re playing a game like this against someone who’s crazy, it’s hard to know what would happen And in fact, a “crazy” player – someone who doesn’t always do what’s best for them – might do better than a “rational” player Because if I’m crazy and I’m firm 2, you might believe that I’ll actually fight if you enter; so you might choose not to enter But if you know I’m rational, then you’re better off entering, since you know that once you enter, I won’t want to fight (Literature on repeated games with reputation, where your actions in the early stages may partly be to try to convince opponents that you’re not a rational player, and therefore that they shouldn’t try to take advantage of you in later stages.) But for us, we’ll stick to the assumption of rationality – I know that if I move first, my opponent will do whatever is in his best interest This is referred to as sequential rationality – since the players are assumed to be rational at each stage of the game

46 Monday, we’ll start in on some particular applications of property law


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