Welfare impact of climate change on capture fisheries in Vietnam

assume that the supply and demand curves have constant price elasticities. Then the demand and supply functions have the following forms: QD ¼ ADPεD or ln QD ¼ ln AD þ εD ln P ð2Þ QS ¼ ASPεS or ln QS ¼ ln AS þ εS ln P ð3Þ in which P is fish price; QD and QS are demand and supply quantities, respectively; AD and AS are constants; and εD and εS are price elasticities of demand and supply, respectively. Since the demand curve slopes downward and the supply curve slopes upward, we have εD < 0 and εS > 0. At the initial state, the price equilibrium is determined at QD0 ¼ QS0 ð4Þ When the relative changes in demand and supply are a and b, respectively (a, b > 1 if the change is an increase; 0 � a, b < 1 if the change is a decrease; a = 1 or b = 1 if there is no change), the new supply and demand functions are as follows: QD1 ¼ aQD0 ð5Þ QS1 ¼ bQS0 ð6Þ The new equilibrium price is identified at QD1 ¼ QS1 ð7Þ Solve the system of Eqs from (2) to (7); we arrive at the relative price change: P1 P0 ¼ a b � � 1 εS εD ð8Þ Change in consumer surplus: DCS ¼ R Pmax P1 aADPεD R Pmax P0 ADPεD ¼ AD 1 þ εD P1þεD 0 aP1þεD 1 � þ ða 1ÞAD 1 þ εD P1þεD max ð9Þ CS1 CS0 ¼ aAD 1þεD P1þεD max P1þεD 1 � AD 1þεD P1þεD max P1þεD 0 � ¼ a 1 P1þεD 1 P1þεD 0 P1þεD max P1þεD 0 � � ð10Þ Change in producer surplus: DPS ¼ R P1 Pmin bASPεS R P0 Pmin ASPεS ¼ AS 1 þ εS bP1þεS 1 P1þεS 0 � ð11Þ PS1 PS0 ¼ að1þεSÞ εS εD bð 1 εDÞ εS εD ð12Þ PLOS ONE Welfare impact of climate change on capture fisheries in Vietnam

PLOS ONE | https://doi.org/10.1371/journal.pone.0264997 April 25, 2022 6 / 20