A model of public and private liquidity integrates financial intermediation theory with a New Monetarist monetary framework. Non-passive fiscal policy and costs of operating a currency system imply that an optimal policy deviates from the Friedman rule. A liquidity trap can exist in equilibrium away from the Friedman rule, and there exists a permanent nonneutrality of money, driven by an illiquidity effect. Financial frictions can produce a financial-crisis phenomenon that can be mitigated by conventional open market operations working in an unconventional manner. Private asset purchases by the central bank are either irrelevant or they reallocate credit and redistribute income.

This paper considers three challenge areas for mechanism design and describes the role approximation plays in resolving them. Challenge 1: optimal mechanisms are finely tuned to precise details of the distribution on agent preferences. Challenge 2: in environments with multi-dimensional agent preferences economic analysis has failed to provide general characterizations optimal mechanisms. Challenge 3: optimal mechanisms are parameterized by unrealistic knowledge of the distribution of agents' private preferences. This paper surveys positive resolutions to these challenges with emphasis on basic techniques and their relevance to theory and practice.

As both a regulator and an academic, Fred Kahn argued that end-use electricity consumers should face prices that reflect the time-varying marginal costs of generating electricity. This has been very slow to happen in the US, even in light of recent technological advances that have lowered costs and improved functionality for meters and automated demand response technologies. We describe these recent developments and discuss the remaining barriers to the proliferation of time-varying electricity pricing.

Popular discussions often treat the great housing boom of the 1996-2006 period as if it were a national phenomenon with similar impacts across locales, but across metropolitan areas, price growth was dramatically higher in warmer, less educated cities with less initial density and higher initial housing values. Within metropolitan areas, price growth was faster in neighborhoods closer to the city center. The centralization of price growth during the boom was particularly dramatic in those metropolitan areas where income is higher away from the city center. We consider a number of different explanations for this connection, and find that the connection between centralized price growth and decentralized income seems to be most explained by the faster price growth in central cities that use relatively more public transit.

Under Medicare Part D, senior citizens choose prescription drug insurance offered by numerous private insurers. We examine nonpoor enrollees' actions in 2006 and 2007 using panel data. Our sample reduced overspending by $298 on average, with gains by 81 percent of them. The greatest improvements were by those who overspent most in 2006 and by those who switched plans. Decisions to switch depended on individuals' overspending in 2006 and on individual-specific effects of changes in their current plans. The oldest consumers and those initiating medications for Alzheimer's disease improved by more than average, suggesting that real-world institutions help overcome cognitive limitations.

That the employment rate appears to respond to changes in trend growth is an enduring macroeconomic puzzle. This paper shows that, in the presence of a return to experience, a slowdown in productivity growth raises reservation wages, thereby lowering aggregate employment. The paper develops new evidence that shows this mechanism is important for explaining the growth-employment puzzle. The combined effects of changes in aggregate wage growth and returns to experience account for all the increase from 1968 to 2006 in nonemployment among low-skilled men and for approximately half the increase in nonemployment among all men.

In 2005, Hurricanes Katrina and Rita forced many children to relocate across the Southeast. While schools quickly enrolled evacuees, families in receiving schools worried about the impacts on incumbent students. We find no effect, on average, of the inflow of evacuees on achievement in Houston. In Louisiana we find little impact on average and we reject linear-in-means models. Moreover, we find that student achievement improves with high achieving peers and worsens with low achieving peers. Finally, an increase in the inflow of evacuees raised incumbent absenteeism and disciplinary problems in Houston's secondary schools.