xBookUtils.terms['fn_25_501'] = "For a good discussion, see Persky, Joseph. 1997. Retrospectives: Classical family values: Ending the poor laws asthey knew them. The Journal of Economic Perspectives 11(1): 179–189.";
xBookUtils.terms['fn_25_502'] = "The proof is slightly involved but not difficult. Suppose that we take away from a consumer a small amount of pizza, ΔPizza, and we give him in return a small amount of gas, ΔGas; then the change in total utility, ΔU, from this exchange is ΔU = –ΔPizza × MUPizza + ΔGas × MUGas. Along an indifference curve, total utility is constant, so ΔU = 0 and thus –ΔPizza × MUPizza + ΔGas × MUGas = 0. Then rearrange to find ΔGas/ΔPizza = MUPizza/MUGas. But ΔGas/ΔPizza is the MRS, the slope of the indifference curve, so we have shown that MRS = MUPizza/MUGas.";
xBookUtils.terms['fn_25_503'] = "If you are following very closely, you may notice that our pickpocket leaves the consumer with just enough income to purchase the old bundle at the point labeled “Old optimum” but our graphical pickpocket takes a little bit more. The first version of the income effect is called the Slutsky income effect, while the second is called the Hicks income effect after its originators. For a small price change, the difference between these two versions of the income effect is slight and can be ignored, which is what we do here.";