Harvard’s Greg Mankiw just keep them coming! Here’s another micro problem from the esteemed professor and textbook author’s blog. Several readers enjoyed challenging themselves with his last Micro problem, so I will re-publish Mankiw’s test question here to see if people can solve it in the comment section on this blog (sorry Professor Mankiw, you have comments turned off on your blog, so how are your readers to know if they have solved it correctly?)

The town of Wiknam has 5 residents whose only activity is producing and consuming fish. They produce fish in two ways. Each person who works on a fish farm raises 2 fish per day. Each person who goes fishing in the town lake catches X fish per day. X depends on N, the number of residents fishing in the lake. In particular, X = 6 – N. Each resident is attracted to the job that pays more fish. a. Why do you suppose that X, the productivity of each fisherman, falls as N, the number of fishermen, rises? What economic term would you use to describe the fish in the town lake? Would the same description apply to the fish from the farms? Explain. b. The town’s Freedom Party thinks every individual should have the right to choose between fishing in the lake and farming without government interference. Under its policy, how many of the residents would fish in the lake and how many would work on fish farms? How many fish are produced? c. The town’s Efficiency Party thinks Wiknam should produce as many fish as it can. To achieve this goal, how many of the residents should fish in the lake and how many should work on the farms? (Hint: Create a table that shows the number of fish produced—on farms, from the lake, and in total—for each N from 0 to 5.) d. The Efficiency Party proposes achieving its goal by taxing each person fishing in the lake by an amount equal to T fish per day and distributing the proceeds equally among all Wiknam residents. Calculate the value of T that would yield the outcome you derived in part (c).

e. Compared with the Freedom Party’s hands-off policy, who benefits and who loses from the imposition of the Efficiency Party’s fishing tax?

The last two years, in which capitalism has suffered one of its periodic shocks, have given John Maynard Keynes a new lease of life. Events have demonstrated the limits of the theory that economies can be relied on to be stable if they are lightly regulated and otherwise left to themselves. There is now much talk of the paradox of thrift, whereby the rational choices of individuals can prove collectively ruinous, and of the need for government to counteract the inherently anarchic tendencies of markets. Keynes has been revived because he understood that markets are very often irrational. Unfortunately, few of those who urge that we go back to him seem to have understood why he believed this.

Apart from a brief postscript to one of the chapters and a few remarks in the preface, George Akerlof and Robert Shiller’s Animal Spirits was written before the current crisis. Yet, based on research undertaken over many years, it can be read as prefiguring the current disillusionment with economics. The trouble with prevailing theories, in Akerlof and Shiller’s view, is that they assume human beings are more rational than they actually are. ‘This book, which draws on an emerging field called behavioural economics, describes how the economy really works,’ they claim. ‘It accounts for how it works when people really are human, that is, possessed of all-too-human animal spirits.’

‘Just as Adam Smith’s invisible hand is the keynote of classical economics,’ they write, ‘Keynes’s animal spirits are the keynote to a different view of the economy – a view that explains the underlying instabilities of capitalism.’ Here they are endorsing the caricature of Smith propagated by neoliberal ideologues anxious to confer a distinguished patrimony on an illegitimate intellectual offspring.