1. Econ 522 Economics of Law Dan Quint Spring 2013 Lectures 17-18

2. 1  MT2 next Monday  Fully cumulative, but more weight on contract law Reminders

3. 2 Recapping our story to date…

4. 3  Efficiency  Maximizing total surplus realized by everyone in society  Scarce resources are owned by whoever values them most  Actions are taken if social benefit exceeds social cost  Design a legal system that leads to efficient outcomes  Once we set up the rules, we don’t expect people to act based on what’s efficient  We expect people to do whatever’s in their own best interest  So the goal is set up the rules such that people acting in their own best interest will naturally lead to efficiency Our story so far

5. 4  Coase gives us one way to do that  If property rights are clearly defined and tradable, and there are no transaction costs, people have incentive to trade until each resource is efficiently owned  So initial allocation of rights doesn’t matter for efficiency  But if there are transaction costs, we may not get efficiency this way  Led us to two normative views of the legal system:  1. Minimize transaction costs (“lubricate” private exchange)  2. Allocate rights as efficiently as possible  Tradeoff between injunctive relief and damages Our story so far

6. 5  Property law works well for simultaneous trade  Contracts allow for non-simultaneous trade  Contract law can…  Enable cooperation  Encourage efficient disclosure of information  Secure optimal commitment to performance  Secure efficient reliance  Supply efficient default rules and regulations  Foster enduring relationships Our story so far

7. 6  So far, we’ve been talking about voluntary exchange  Coase is predicated on exchange being voluntary for both parties  Contracts are an extension of voluntary trade  Up next: “involuntary trade”  You’re bicycling to class, I’m texting while driving and I hit you  You didn’t want to deal with me, I didn’t want to deal with you… Our story so far

8. 7  To put it another way…  Property law covers situations where transaction costs are low enough to get agreement ahead of time  Exceptions to property law – private necessity, eminent domain – when this isn’t the case  Contract law covers situations when transaction costs are low enough for us to agree to a contract, high enough that we may not want to renegotiate the contract later  Tort law covers situations where transaction costs are too high to agree to anything in advance Our story so far

9. 8 Tort law

10. 9 An example

11. 10 An example ChoiceBad LuckOutcome +  punish the choice criminal law regulations

12. 11 An example ChoiceBad LuckOutcome +  punish the choice criminal law regulations punish the combination of choice and outcome “negligence” punish the outcome “strict liability”

13. 12  Tort, noun. from French word meaning injury  Contract law: situations where someone harms you by breaking a promise they had made  Tort law: situations where someone harms you without having made any promises  “If someone shoots you, you call a cop. If he runs his car into yours, you call a lawyer.” Tort law

14. 13  I hit you with my car, do $1,000 worth of damage  You’re $1,000 worse off  (No damage to me or my car)  Should I have to pay you damages? As always, we’ll be focused on achieving efficiency –1,000 Combined payoffs –50,000–1,0000My payoff 49,0000–1,000Your payoff I owe $50,000I owe $1,000I owe nothing

15. 14 Something to remember distribution but not efficiency efficiency

16. 15  Question: how to structure the law to get people to behave in a way that leads to efficient outcomes?  Deliberate harms: make punishment severe (criminal law)  Accidental harms: trickier  Goal isn’t “no accidents”; goal is “efficient number of accidents” Tort law

17. 16  Question: how to structure the law to get people to behave in a way that leads to efficient outcomes?  Deliberate harms: make punishment severe (criminal law)  Accidental harms: trickier  Goal isn’t “no accidents”; goal is “efficient number of accidents”  Unlike nuisance law, injunctive relief is not an option  Unlike contract law, no agreement ahead of time  Cooter and Ulen: essence of tort law is “the attempt to make injurers internalize the externalities they cause, in situations where transaction costs are too high to do this through property or contract rights” Tort law

18. 17  Plaintiff – person who brings a lawsuit  Defendant – person who is being sued  In a nuisance case, the defendant caused a nuisance, plaintiff was bothered by it, might be asking for injunction or damages  In a contract case, defendant breached a contract or violated its terms  In a tort case, defendant caused some harm to plaintiff, plaintiff is asking for damages  Plaintiff is the victim (person who was harmed)  Defendant is the injurer (person who caused the harm) Cast of characters

19. 18  Harm  Causation  Breach of Duty “Classic” legal theory of torts

20. 19  For a tort to exist, the plaintiff needs to have been harmed  “Without harm, there is no tort”  Gas company sold gas with a defective additive  Dangerous for cars with turbocharged carburetors  You have a car with normal carburetors  You might be angry; but you weren’t harmed, so you can’t sue  Similarly, no compensation for exposure to risk  Manufacturer exposed workers to some chemical  Exposure will cause 15% of them to develop cancer later in life  Can’t sue now – have to wait, see who gets cancer, then they can sue Element 1: Harm

21. 20 Element 1: Harm Money Health  Perfect compensation  restores victim to original level of well-being  generally done through money damages

22. 21 Perfect Compensation Emotional harm Pain and suffering Loss of companionship Medical costs Lost income Damaged property Intangible harmsTangible harms  In theory, perfect compensation should cover all losses  Historically, courts have been less willing to compensate for intangible or hard-to-measure losses  Over time, U.S. courts have started compensating for more intangible harms  Pro: the closer liability is to actual harm done, the better the incentive to avoid these harms  Con: disparity in award sizes, unpredictability

23. 22  Harm  Causation  Breach of Duty “Classic” legal theory of torts

24. 23  For a tort to exist, the defendant needs to have caused the harm to the plaintiff  Cause-in-fact  “But for the defendant’s actions, would the harm have occurred?” Element 2: Causation

25. 24  For a tort to exist, the defendant needs to have caused the harm to the plaintiff  Cause-in-fact  “But for the defendant’s actions, would the harm have occurred?”  Proximate cause  Immediate cause – defendant’s action can’t be too distant from the harm  Palsgraf v Long Island Railway (NY Ct Appeals, 1928):  Guard pushed a passenger to help him onto train, passenger dropped fireworks he was carrying, they went off, explosion knocked down scales at the other end of the platform, which fell on Mrs. Palsgraf  Guard’s actions were not the proximate cause Element 2: Causation

26. 25 “A tree fell on a moving trolly, injuring passengers. One of them sued. He succeeded in demonstrating that in order for the trolly to be where it was when the tree fell on it the driver had to have driven faster than the speed limit at some point during the trip. Breaking the law is per se negligence, so the driver was legally negligent whether or not his driving was actually unsafe. If he had not driven over the speed limit, the trolly would not have been under the tree when it fell, so, the plaintiff argued, the driver’s negligence caused the injury.”  Court ruled driver’s negligence “had not caused the accident in the legally relevant sense” Element 2: Causation

27. 26  Harm  Causation  Breach of Duty “Classic” legal theory of torts

28. 27 Element 3: Breach of Duty Harm Causation Breach of duty (fault) Harm Causation NegligenceStrict Liability  When someone breaches a duty he owes to the defendant, and this leads to the harm, the injurer is at fault, or negligent  Injurers owe victims the duty of due care  Negligence rule: I’m only liable if I failed to take the required standard of care – not if I was careful and the accident happened anyway (Sometimes required, sometimes not)

29. 28 “A tree fell on a moving trolly, injuring passengers. One of them sued. He succeeded in demonstrating that in order for the trolly to be where it was when the tree fell on it the driver had to have driven faster than the speed limit at some point during the trip. Breaking the law is per se negligence, so the driver was legally negligent whether or not his driving was actually unsafe. If he had not driven over the speed limit, the trolly would not have been under the tree when it fell, so, the plaintiff argued, the driver’s negligence caused the injury.” Hence the language in the trolly example

30. 29  If I breach my duty of due care and injure you, I am liable  If I exercise the appropriate level of care but still injure you, I’m not liable  How is the standard of care determined?  That is, how careful do I have to be to avoid liability, and who decides?  Is it negligent to drive 40 MPH on a particular road at a particular time of day? What about 41 MPH? 42? So under a negligence rule…

31. 30  Some settings: government imposes safety regulations that are also used as standard for negligence  Speed limits for highway driving  Requirement that bicycles have brakes  Workplace regulations  Some standards are left vague  “Reckless driving” may depend on road, time of day, weather…  Common law focuses on duty of reasonable care  Level of care a reasonable person would have taken  (Civil law relies less on “reasonableness” tests, tries to spell out what level of care is required) How is the standard of care determined?

32. 31  Strict liability rule: plaintiff must prove harm and causation  Negligence rule: must prove harm, causation, and negligence  A little history  Early Europe: strict liability was usual rule  By early 1900s, negligence became usual rule  Second half of 1900s, strict liability became more common again, especially for manufacturer liability in American consumer products  U.S. manufacturers now held liable for harms caused by defective products, whether or not they were at fault Strict liability versus negligence

33. 32  Harm  Causation  Breach of Duty “Classic” legal theory of torts

34. 33  Like with contract law, our main concern is with the incentives created by liability rules  So… what incentives are we interested in? Next question

35. 34 Precaution

36. 35  The more carefully I drive, the less likely I am to hit you  But, driving more carefully is also more costly to me  Must be some efficient level of care  Similarly…  Construction company can reduce accidents with better safety equipment, better training, working shorter days, all of which cost money  Manufacturer can reduce accidents by designing/inspecting products more carefully – again, more expensive Precaution

37. 36 Actions by both injurer and victim impact number of accidents drive carefully drive drunk while texting careful quality control cheap, hasty manufacturing install smoke detectors, other safety equipment save money drive slowly speed like hell wear helmet and use light bicycle at night wearing black GREATER EFFORT TO PREVENT ACCIDENTS LESS EFFORT TO PREVENT ACCIDENTS “MORE PRECAUTION”“LESS PRECAUTION”

38. 37  Precaution: anything either injurer or victim could do to reduce likelihood of an accident (or damage done)  The next two questions should be obvious…  How much precaution do we want?  What is efficient level of precaution?  How do we design the law to get it? We will call all these things precaution

39. 38  Car hits a bicycle  In real life: driver probably has insurance  In real life: some damage to bicycle, some damage to driver’s car  In real life: driver and bicyclist may not even know what the law is  We’ll simplify things a lot, by assuming…  Only one party is harmed  Parties know the law, don’t have insurance (for now)  We’ll focus on one party’s precaution at a time To answer these questions, we’ll introduce a very simple model of accidents

40. 39 Simple economic model for thinking about tort law

41. 40  Unilateral harm – just one victim  Precaution – costly actions that make accident less likely  Could be taken by either victim or injurer  We’ll consider both, but one at a time  Notation  x – the amount of precaution that is taken  w – the cost of each “unit” of precaution  so total cost of precaution is wx  p(x) – probability of an accident, given precaution x  p is decreasing in x  A – cost of accident (to victim)  so expected cost of accidents is p(x) A Model of unilateral harm x level of precaution w marginal cost of precaution p(x) probability of an accident A cost of an accident

42. 41 Model of unilateral harm x level of precaution w marginal cost of precaution p(x) probability of an accident A cost of an accident Precaution (x) $ p(x) A (Cost of Accidents) wx (Cost of Precaution) wx + p(x) A (Total Social Cost) x* (Efficient Level of Precaution) efficient precaution: min x { wx + p(x) A } w + p’(x) A = 0 w= – p’(x) A marginal social cost of precaution marginal social benefit of precaution x < x*x > x*

43. 42 A technical note (clarification)  We’re thinking of bilateral precaution, just “one at a time”  So really, x injurer, x victim, problem is min xi, xv { p(x i, x v ) A – w i x i – w v x v }  “Hold fixed” one party’s action and consider the other: min xi { p(x i, x v ) A – w i x i – w v x v } given x v (and v.v.) This has same solution as min xi { p(x i, x v ) A – w i x i }  Our result will generally be “efficient given what the other guy is doing”

44. 43  We know what’s efficient  Level of precaution that minimizes total social cost = wx + p(x) A  We’ll consider what happens if there is…  no liability rule in place  a strict liability rule  a negligence rule Effect of liability rules on precaution

45. 44 Benchmark: what happens without any liability rule? (we’ll probably stop here)

46. 45  In a world with no liability…  Injurer does not have to pay for accidents  So, bears cost of any precautions he takes, but does not receive any benefit  Injurer has no incentive to take precaution  Victim bears cost of any accidents, plus cost of precaution he takes  (Victim precaution imposes no externality on injurer)  Victim precaution will be efficient Benchmark: No Liability

47. 46  Injurer’s private cost is just wx  Minimized at x = 0  Victim’s private cost is p(x) A + wx  Minimized at efficient precaution level x = x*  So rule of no liability leads to efficient precaution by victims, no precaution by injurers Benchmark: No Liability x $ p(x) A wx wx + p(x) A x* Private cost to injurer Private cost to victim

48. 47 Benchmark: No Liability EfficientZeroNo Liability Victim Precaution Injurer Precaution

49. 48  Precaution – actions which make an activity less dangerous  Driving carefully  Wearing bright-colored clothing while bicycling  The amount we do each activity also affects the number of accidents  I decide how much to drive  You decide how much to bicycle  Liability rules create incentives for activity levels as well as precaution Precaution isn’t the only thing that determines number of accidents

50. 49  With no liability, I’m not responsible if I hit you  I don’t consider cost of accidents when deciding how fast to drive…  …and I also don’t consider cost of accidents when deciding deciding how much to drive  So I drive too recklessly, and I drive too much  (or: if there is no liability, social cost of driving includes cost of accidents, but private cost to me does not;  driving imposes negative externality, so I do it too much)  So with no liability, injurer’s activity level is inefficiently high With no liability rule…

51. 50  With no liability, victim bears full cost of accidents  Greater activity by victim (more bike-riding) leads to more accidents  Victim weighs cost of accidents when deciding how carefully to ride, and when deciding how much to ride  (Private cost = social cost)  Victim takes efficient level of precaution, and efficient level of activity  A rule of no liability leads to an inefficiently high level of injurer activity, but the efficient level of victim activity What about victims?

52. 51 Benchmark: No Liability EfficientToo HighEfficientZeroNo Liability Victim Activity Injurer Activity Victim Precaution Injurer Precaution

53. 52 Next: what happens under a strict liability rule?

54. 53  Perfect compensation: damages D = A  Under strict liability…  Injurer pays damages for any accidents he causes  So injurer bears cost of accidents, plus his own precaution  Injurer internalizes externality his actions cause  chooses efficiently  Victim is fully insured, no incentive for precaution Strict Liability

55. 54  (Damages = A)  Injurer’s private cost is p(x) A + wx  Minimized at efficient precaution level x = x*  Victim’s private cost is just wx  Minimized at x = 0  So rule of strict liability leads to efficient precaution by injurers, no precaution by victims Strict Liability x $ p(x) A wx wx + p(x) A x* Private cost to injurer Private cost to victim

56. 55 Strict Liability ZeroEfficientStrict Liability EfficientToo HighEfficientZeroNo Liability Victim Activity Injurer Activity Victim Precaution Injurer Precaution

57. 56  Under strict liability, injurer internalizes cost of accidents  Weighs benefit from driving against cost of accidents  Takes efficient activity level  Under strict liability, victim does not bear cost of accidents  Ignores cost of accidents when deciding how much to bike  Sets inefficiently high activity level  A rule of strict liability leads to the efficiently level of injurer activity, but an inefficiently high level of victim activity What about activity level?

58. 57 Strict Liability Too HighEfficientZeroEfficientStrict Liability EfficientToo HighEfficientZeroNo Liability Victim Activity Injurer Activity Victim Precaution Injurer Precaution

59. 58  For both precaution and activity level…  “No liability” leads to inefficient behavior by injurer, efficient behavior by victim  “Strict liability” leads to efficient behavior by injurer, inefficient behavior by victim  Reminiscent of paradox of compensation  One rule sets multiple incentives…  …can’t get them all right  But in tort law, we have a trick… So…

60. 59 Negligence (won’t get to)

61. 60  Negligence rule: injurer is liable if he breached the duty of due care  Within our model:  Legal standard of care x n  Injurer owes damages if precaution level was below that level  x < x n  D = A  x  x n  D = 0  So on our graph from before, private cost to injurer is…  wx + p(x) Afor x < x n  wxfor x  x n  Best shot at achieving efficiency is to set x n = x* Negligence Rule

62. 61 “Simple Negligence”: Injurer precaution x $ p(x) A wx wx + p(x) A x n = x*  Private cost is wx + p(x) A if x < x n, only wx otherwise  If standard of care is set efficiently (x n = x*), injurer minimizes private cost by taking efficient precaution Private cost to injurer

63. 62 “Simple Negligence”: Victim precaution $ p(x) A wx wx + p(x) A x*  What about victim?  We just said, injurer will take efficient precaution  Which means injurer will not be liable  So victim bears costs of any accidents  (Victim bears residual risk)  So victim’s private cost is wx + p(x) A  Victim minimizes private cost by taking efficient level of precaution too! Private cost to victim (assuming injurer takes efficient level of precaution and is therefore not liable for damages)

64. 63 Simple Negligence Efficient Simple Negligence, x n = x* Too HighEfficientZeroEfficientStrict Liability EfficientToo HighEfficientZeroNo Liability Victim Activity Injurer Activity Victim Precaution Injurer Precaution

65. 64  Rule we just saw is called “simple negligence”  Only consider injurer’s actions in determining liability  But we could also consider whether victim was negligence in deciding whether injurer is liable  “Negligence with a defense of contributory negligence” – injurer owes nothing if victim was also negligent  “Comparative negligence” – if both were negligent, share cost  “Strict liability with defense of contributory negligence” – injurer is liable (even if he wasn’t negligence), unless victim was negligent  Any of these rules (with efficient standard of care) will lead to efficient precaution by both parties! Other negligence rules

66. 65  No “levels” of precaution – each party can either take precaution or not  Each accident causes $1,000 of harm  Precaution costs $20 for each party  Chance of an accident is  10% if nobody takes precaution  6% if one party takes precaution  2% if both parties take precaution  Note that precaution is efficient for both parties  Costs $20; reduces expected accidents by 4% X $1,000 = $40 Discrete example of bilateral precaution A$1,000 w$20 for either party p10% / 6% / 2%

67. 66 Different negligence rules NoYesNo Negligence with Defense of Contributory Negligence Yes No Simple Negligence Both parties negligent? Only injurer negligent? Only victim negligent? Neither party negligent? Does injurer owe victim damages when… A$1,000 w$20 for either party p10% / 6% / 2%

68. 67  Injurer is liable if he failed to take precaution…  Unless victim did too  Precaution is always best-response for victim  If injurer is not taking precaution, victim wants to avoid liability  If injurer is taking precaution, victim bears residual risk, wants to minimize accidents  For injurer, precaution is the best-response to precaution  “Both take precaution” is the only Nash equilibrium  And, is the efficient outcome Negligence with a Defense of Contributory Negligence -20, -40-20, -60 -60, -200, -100 PrecautionNone Precaution None Victim Injurer A$1,000 w$20 for either party p10% / 6% / 2% injurer pays for precaution, not liable for accidents victim pays for precaution, and any accidents that happen

69. 68 Different negligence rules PartialYesNo Comparative Negligence NoYesNo Negligence with Defense of Contributory Negligence Yes No Simple Negligence Both parties negligent? Only injurer negligent? Only victim negligent? Neither party negligent? Does injurer owe victim damages when… A$1,000 w$20 for either party p10% / 6% / 2%

70. 69  If both parties were negligent…  …divide cost proportionally  Precaution is again a dominant strategy for victim  Now it’s a dominant strategy for injurer too  Again, “both take precaution” is the only equilibrium  (And the efficient outcome) Comparative Negligence -20, -40-20, -60 -60, -20-50, -50 PrecautionNone Precaution None Victim Injurer A$1,000 w$20 for either party p10% / 6% / 2%

71. 70 Different negligence rules NoYesNoYes Strict Liability with Defense of Contributory Negligence PartialYesNo Comparative Negligence NoYesNo Negligence with Defense of Contributory Negligence Yes No Simple Negligence Both parties negligent? Only injurer negligent? Only victim negligent? Neither party negligent? Does injurer owe victim damages when… A$1,000 w$20 for either party p10% / 6% / 2%

72. 71  Now, injurer is liable, regardless of whether he took precaution…  …unless victim was negligent  Once again, “both take precaution” is the only equilibrium Strict Liability with a Defense of Contributory Negligence -40, -20-20, -60 -60, -200, -100 PrecautionNone Precaution None Victim Injurer A$1,000 w$20 for either party p10% / 6% / 2%

73. 72 Negligence Efficient Negligence with a Defense of Contributory Negligence Efficient Strict Liability with Defense of Contributory Negligence Efficient Comparative Negligence Efficient Simple Negligence Too HighEfficientZeroEfficientStrict Liability EfficientToo HighEfficientZeroNo Liability Victim Activity Injurer Activity Victim Precaution Injurer Precaution assuming all relevant standards of care are set to the efficient levels

74. 73  Simple negligence: injurer is only liable if he was negligent  Leads injurer to take efficient precaution, so injurer expects to not be liable for any accidents that do occur  So injurer ignores cost of accidents when deciding on activity level (how much to drive)  Injurer drives carefully, but still drives too much  Victim bears “residual risk”  Victim bikes carefully, and bikes efficient amount What about activity levels under a negligence rule?

75. 74 Adding activity levels to our results on precaution… Efficient Negligence with a Defense of Contributory Negligence Efficient Strict Liability with Defense of Contributory Negligence Efficient Comparative Negligence EfficientToo HighEfficient Simple Negligence Too HighEfficientZeroEfficientStrict Liability EfficientToo HighEfficientZeroNo Liability Victim Activity Injurer Activity Victim Precaution Injurer Precaution

76. 75  Either rule: efficient precaution by both parties  Either rule: if neither party was negligent, injurer does not owe damages  So victim is residual risk bearer (pays for accidents)  So victim weighs cost of accidents against benefits of activity, takes efficient activity level  Injurer ignores cost of accidents, takes inefficiently high activity level Negligence with Defense of Contributory Negligence, and Comparative Negligence

77. 76 Negligence EfficientToo HighEfficient Negligence with a Defense of Contributory Negligence Efficient Strict Liability with Defense of Contributory Negligence EfficientToo HighEfficient Comparative Negligence EfficientToo HighEfficient Simple Negligence Too HighEfficientZeroEfficientStrict Liability EfficientToo HighEfficientZeroNo Liability Victim Activity Injurer Activity Victim Precaution Injurer Precaution

78. 77  If victim is not negligent, injurer is liable  Leads to efficient precaution by both, so injurer is liable  Injurer is residual risk bearer  Injurer weighs cost of accidents against benefits of activity, takes efficient activity level  Victim ignores cost of accidents, takes inefficient high activity level Strict Liability with Defense of Contributory Negligence

79. 78 Negligence EfficientToo HighEfficient Negligence with a Defense of Contributory Negligence Too HighEfficient Strict Liability with Defense of Contributory Negligence EfficientToo HighEfficient Comparative Negligence EfficientToo HighEfficient Simple Negligence Too HighEfficientZeroEfficientStrict Liability EfficientToo HighEfficientZeroNo Liability Victim Activity Injurer Activity Victim Precaution Injurer Precaution

80. 79 An easier (perhaps) way to understand all of this EfficientToo HighEfficient Negligence with a Defense of Contributory Negligence Too HighEfficient Strict Liability with Defense of Contributory Negligence EfficientToo HighEfficient Comparative Negligence EfficientToo HighEfficient Simple Negligence Too HighEfficientZeroEfficientStrict Liability EfficientToo HighEfficientZeroNo Liability Victim Activity Injurer Activity Victim Precaution Injurer Precaution take precaution only to AVOID liability precaution is efficient, but activity level is too high

81. 80 An easier (perhaps) way to understand all of this EfficientToo HighEfficient Negligence with a Defense of Contributory Negligence Too HighEfficient Strict Liability with Defense of Contributory Negligence EfficientToo HighEfficient Comparative Negligence EfficientToo HighEfficient Simple Negligence Too HighEfficientZeroEfficientStrict Liability EfficientToo HighEfficientZeroNo Liability Victim Activity Injurer Activity Victim Precaution Injurer Precaution to reduce accidents, since he bears their cost precaution and activity level are both efficient

82. 81  One party can avoid liability by taking efficient precaution  Leads to efficient precaution  But inefficient activity level  Other party is the residual risk bearer – even when he takes precaution, he is still liable  Leads to efficient precaution  And also efficient activity level  Who should bear residual risk?  One way to answer is to ask whose activity level has greater impact on efficiency With each negligence rule…

83. 82  “Put the incentive where it does the most good”  Efficient rule depends on which choices have greatest impact  If only injurer’s choices (precaution + activity) matter  strict liability is better rule  If bilateral precaution  negligence  Which negligence rule – depends whose activity level is more important  Friedman (citing Posner): this is why very dangerous activities often covered by strict liability  Blasting with dynamite, keeping a lion as a pet  Even with proper precaution, still very dangerous, so injurer activity level is important So which rule is best?

84. 83  Activity is just another type of precaution, but type where court can’t determine efficient level  Court can tell inefficient for me to drive at night with headlights off  Can’t tell how many miles it’s efficient for me to drive  Determination of negligence can only be based on observable precaution, not unobservable  Negligence rule leads to efficient levels of observable precaution by both parties  Simple negligence leads only to efficient observable precaution by injurer, but efficient precaution by victim as well  Strict liability leads to efficient observable and unobservable precaution by injurer, but no precaution by victim Friedman: activity is just unobservable precaution