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Valuation 2 and 3: Demand and welfare theory What is so special about environmental goods? Theory of consumer demand for market goods Welfare effects of a price change: Equivalent variation versus compensating variation Consumer demand for environmental goods Welfare effects of a quantity change: Equivalent surplus versus compensating surplus Theory and practise

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Last week Price and Value Total Economic Value Why and what to value? Uses of economic valuation

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Why valuation? We must make choices about how to manage the human impact on natural systems Greater use of a particular environmental service or greater protection of a specific natural system results in less of something else (trade-off) To make the most of scarce resources we must compare what is gained from an activity with what is sacrificed by undertaking that activity Why? To assess the net impact of changes

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What is so special about environmental goods and services? In economics the criterion for assessing the net impacts („benefits“ and „costs“ ) is the well-being of the members of society Well-being is defined as the individuals‘ preferences for goods Preferences are typically represented through demand functions –Changes in well-being can be inferred by changes in prices or quantity Problem with environmental goods: no markets exist –Individuals have preferences nevertheless Changes in well-being are derived by individuals’ –max. willingness to pay for gains or (WTP) –min. willingness to accept compensation for losses (WTA) Prices and marginal WTP or WTA are equivalent

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Consumer demand theory: Market goods Consider a consumer who has a utility function This consumer maximises the utility of a bundle of goods x, with prices p, and income M This solves to the ordinary or Marshallian demand function Substituting the expression for x i gives the indirect utility function –this gives you the highest level of utility attainable, given prices p and income Y

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Consumer demand theory -2 Roy‘s identity relates x and v: That is, the derivative of indirect utility with respect to the ith price yields the ith demand function, after normalising by the marginal utility of income

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Constructing an ordinary demand function A B C I1I1 I2I2 I3I3 p1p1 C A B x 1 (p 1,p 2,y), demand for x 1 Budget constraint x1x1 x1x1 x2x2

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Consumer demand theory -3 An alternative to generate a demand curve is to keep utility constant instead of income Here the consumer is assumed to minimize total expenditure to achieve a given level of utility at price level P This solves to the compensated or Hicksian demand function This gives the quantity demanded as a function of price and utility Income is of no consequence; as prices change, expenditures are adjusted to maintain constant utility.

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Consumer demand theory -4 Demand for the ith commodity is the derivative of the expenditure function to the price of i

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Constructing a compensated demand function A B C I1I1 C A B h x1 (p 1,p 2,U 1 ), demand for x 1 Budget constraint p1p1 x1x1 x1x1 x2x2

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Ordinary and compensated demand We derived ordinary and compensated demand functions Ordinary demand functions bundle income and price effects together Compensated demand function do not have this problem, but look at price effects alone To evaluate the effect of a governmental policy that changes relative prices we want to examine the price effect only Typically, economists estimate ordinary demand functions, as utility cannot be observed

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Income and price effects A B x2x2 x1x1 Price effect e/p 2 1 Income effect C D I1I1 I0I0 e/p 2 2 M

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Surplus from ordinary and compensated demand A B p1p1 x1x1 If AB is an ordinary demand function like x 1 (p 1,p 2,M): Consumer Surplus= ABCD-BCDE=ABE E p* 1 x* 1 If AB is a compensated demand function like h x1 (p 1,p 2,U 1 ) the area under the curve correspond to changes in constant utility expenditures CD

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Ordinary and compensated demand - 3 A B h x1 (p 1,p 2,U 1 ) x 1 (p 1,p 2,M) p1p1 x1x1 h x1 (p 1,p 2,U 0 ) Ordinary demand Compensated demand

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Ordinary and compensated demand - 4 Properties of both demand functions are related We observe ordinary demand functions, but we are interested in compensated demand functions – the latter can be derived from the former if agents are rational, and even then it involves many steps including integration

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Welfare effects of price changes Consider price fall P* P # Willingness to pay (WTP) to secure price fall is known as compensating variation (CV) Willingness to accept compensation (WTAC) to forego price fall is known as equivalent variation There are gains and loss, so four measures (EV) –Price decreases WTP to secure a gain (CV) WTAC to forego a gain (EV) –Price increases WTP to prevent a loss (EV) WTAC to tolerate a loss (CV)

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Welfare measures Compensating variation is the quantity of income that compensates consumers for a price change, that is, returns them to their original welfare Equivalent variation is an income change that yields the same utility change as the price change Both terms can be defined using the expenditure function

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Ordinary and compensated demand: Welfare effects B h x1 (p 1,p 2,U 1 ) x 1 (p 1,p 2,M) p1p1 x1x1 h x1 (p 1,p 2,U 0 ) Ordinary demand Compensated demand A G F D E x01x01 x11x11 p11p11 p01p01 Compensated variation: ABEG Consumer Surplus: AEFB Equivilent variation: ADFB => If p decreases CV< CS

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Consumer demand theory: Environmental goods Often demand for environmental commodities is only indirectly observed People change their behaviour in response to changes in the environment, but do not purchase environmental quality directly We‘ll repeat the analysis above, but now assume that only n-1 goods are directly traded; the nth good (named q) is the environmental commodity of interest

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Restricted demand The environmental good q affects individuals utility This consumer maximises the utility of a bundle of goods X, with prices P, and income M This leads to restricted ordinary demand functions and a restricted indirect utility Again, Roy‘s identity relates x and v

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Restricted demand - 2 The dual of the problem: Minimising expenditure This leads to the expenditure function function The Hicks-compensated demand function for changes in prices is The Hicks-compensated inverse demand (marginal WTP) for changes in q is Rearranging the equation yields the compensating demand for q

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Restricted demand - 3 But... we can determine how expenditures change with q for some price of good x and implicitly defining a demand function for q only if we assume weak complementarity That is, if the demand for good x drops to zero, then demand for good q goes to zero as well and marginal changes in q no longer affect expenditure Example: if swimming is too expensive, water quality is irrelevant

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Restricted compensated demand Choke price p1p1 x1x1 p* 1 h x1 (p 1,q 0,U 1 ), initial demand for x 1 C D A B h x1 (p 1,q 0 + q,U 1 ), demand for x 1 after increase in q The income equivalent or marginal WTP for a change in q: ABC

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Welfare effects of quantity changes Measures of „surplus“ instead of „variation“ when consumers are not free to vary the quantity of q In case of quantity changes, compensating and equivalent surplus are defined as U 0 results from (P,q 0,M)

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Measures of changes in welfare for an environmental good A B C D U1U1 U2U2 q0q0 q1q1 M M=p x x Expenditure on private good x, M Quantity/quality of environmental good q U3U3 CS/p x ES/p x If q 0 increases to q 1, income has to be reduced by CS/p to keep the same utility

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WTP and WTAC If the good is relatively unimportant ES and CS are roughly the same If environmental goods are relatively scarcer than market commodities, one may expect the compensating variation/surplus (WTP) to be smaller than the equivalent variation/surplus (WTAC) for improvements Differences between WTP and WTAC are mainly due to income effects People view gains and losses differently –WTP is limited to an individual‘s income, WTAC is unbounded –Confirmed by empirical studies, but not uncontested –Implies that surveys, policies need to be carefully designed Income effects are small only if the good is of little value relative to your overall wealth

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Theory and practice Horowitz and McConnell collect 208 observations of WTP and WTAC from 45 studies For all studies, the average ratio WTAC/WTP is 7.2 (0.9) However, for public or non-market goods, the ratio is 10.4 (2.5) For ordinary goods, it is 2.9 (0.3) For money, it is 2.1 (0.2)

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Methods for measuring demand Indirect methods (use values) –Surrogate market where we observe expenditures on a related goods –Infer information on the trade-off between money and the environmental good –Hedonic pricing –Household production function approach Direct methods (use and non-use values) –Hypothetical/constructed market –Contingent valuation: “value contingent on there being a market” –Choice modelling

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