Knowledge that Transforms

In 2003 the federal-state Medicaid program provided prescription drug coverage to more than 50 million people. To determine the price that it will pay for each drug, Medicaid uses the average private sector price. When Medicaid is a large part of the demand for a drug, this creates an incentive for its maker to increase prices for other health care consumers. Using drug utilization and expenditure data for the top 200 drugs in 1997 and in 2002, we investigate the relationship between the Medicaid market share (MMS) and the average price of a prescription. Our estimates imply that a 10-percentage-point increase in the MMS is associated with a 7 to 10 percent increase in the average price of a prescription. In addition, the Medicaid rules increase a firm's incentive to introduce new versions of a drug in order to raise price. We find empirical evidence that firms producing newer drugs with larger sales to Medicaid are more likely to introduce new versions. Taken together, our findings suggest that government procurement rules can alter equilibrium price and product proliferation in the private sector.

We examine how people form social networks among their peers. We use a unique data set that tells us the volume of email between any two people in the sample. The data are from students and recent graduates of Dartmouth College. First-year students interact with peers in their immediate proximity and form long-term friendships with a subset of these people. This result is consistent with a model in which the expected value of interacting with an unknown person is low (making traveling solely to meet new people unlikely), while the benefits from interacting with the same person repeatedly are high. Geographic proximity and race are greater determinants of social interaction than are common interests, majors, or family background. Two randomly chosen White students interact three times more often than do a Black student and a White student. However, placing the Black and White student in the same freshman dorm increases their frequency of interaction by a factor of three. A traditional “linear in group means” model of peer ability is only a reasonable approximation to the ability of actual peers chosen when we form the groups around all key factors including distance, race and cohort.

Managers appear to manipulate firm earnings through their characterizations of pension assets to capital markets and alter investment decisions to justify, and capitalize on, these manipulations. Managers are more aggressive with assumed long-term rates of return when their assumptions have a greater impact on reported earnings. Firms use higher assumed rates of return when they prepare to acquire other firms, when they are near critical earnings thresholds, and when their managers exercise stock options. Changes in assumed returns, in turn, influence pension plan asset allocations. Instrumental variables analysis indicates that 25 basis point increases in assumed rates are associated with 5 percent increases in equity allocations.

How does the formation of cross-country teams affect the organization of work and the structure of wages? To study this question, we propose a theory of the assignment of heterogeneous agents into hierarchical teams, where less skilled agents specialize in production and more skilled agents specialize in problem solving. We first analyze the properties of the competitive equilibrium of the model in a closed economy, and show that the model has a unique and efficient solution. We then study the equilibrium of a two-country model (North and South), where countries differ in their distributions of ability, and in which agents in different countries can join together in teams. We refer to this type of integration as globalization. Globalization leads to better matches for all southern workers but only for the best northern workers. As a result, we show that globalization increases wage inequality among nonmanagers in the South, but not necessarily in the North. We also study how globalization affects the size distribution of firms and the patterns of consumption and trade in the global economy.

We analyze a randomized experiment in which 14,000 tax filers in H&R Block offices in St. Louis received matches of zero, 20 percent, or 50 percent of IRA contributions. Take-up rates were 3 percent, 8 percent, and 14 percent, respectively. Among contributors, contributions, excluding the match, averaged $765 in the control group and $1100 in the match groups. Taxpayer responses to similar incentives in the Saver's Credit are much smaller. Taxpayers did not game the experiment by receiving a match and strategically withdrawing funds. Tax professionals significantly influenced contribution choices. These results suggest that both incentives and information affect behavior.

Recent HIV treatment breakthroughs have lowered HIV mortality in the United States, but have also coincided with increased HIV incidence. We argue that these trends are causally linked, because new treatments have improved health and survival for the HIV +, increased their sexual activity, and thus facilitated HIV's spread. Using variation in state-level Medicaid eligibility rules as an instrument for HIV treatment, we find that treating HIV + individuals more than doubles their number of sex partners. A change of this magnitude would increase infection risk by at least 44 percent for the HIV-negative and likely have lowered their expected welfare.

This paper provides an explanation for the run-up of U. S. inflation in the 1960s and 1970s and the sharp disinflation in the early 1980s, which standard macroeconomic models have difficulties in addressing. I present a model in which rational policy-makers learn about the behavior of the economy in real time and set stabilization policy optimally, conditional on their current beliefs. The steady state associated with the self-confirming equilibrium of the model is characterized by low inflation. However, prolonged episodes of high inflation ending with rapid disinflations can occur when policy-makers underestimate both the natural rate of unemployment and the persistence of inflation in the Phillips curve. I estimate the model using likelihood methods. The estimation results show that the model accounts remarkably well for the evolution of policy-makers' beliefs, stabilization policy, and the postwar behavior of inflation and unemployment in the United States.

"This study develops theory and uses a door-to-door fundraising field experiment to explore the economics of charity. We approached nearly 5000 households, randomly divided into four experimental treatments, to shed light on key issues on the demand side of charitable fundraising. Empirical results are in line with our theory: in gross terms, our lottery treatments raised considerably more money than our voluntary contributions treatments. Interestingly, we find that a one standard deviation increase in female solicitor physical attractiveness is similar to that of the lottery incentive, the magnitude of the estimated difference in gifts is roughly equivalent to the treatment effect of moving from our theoretically most attractive approach (lotteries) to our least attractive approach (voluntary contributions)"--National Bureau of Economic Research web site.

There is widespread evidence supporting the conjecture that borrowing constraints have important implications for firm growth and survival. In this paper we model a multiperiod borrowing/lending relationship with asymmetric information. We show that borrowing constraints emerge as a feature of the optimal long-term lending contract, and that such constraints relax as the value of the borrower's claim to future cash flows increases. We also show that the optimal contract has interesting implications for firm dynamics. In agreement with the empirical evidence, as age and size increase, mean and variance of growth decrease, and firm survival increases.

A continuum of ages exists at school entry due to the use of a single school cutoff date—making the “oldest” children approximately 20 percent older than the “youngest” children. We provide substantial evidence that these initial maturity differences have long-lasting effects on student performance across OECD countries. In particular, the youngest members of each cohort score 4–12 percentiles lower than the oldest members in grade four and 2–9 percentiles lower in grade eight. In fact, data from Canada and the United States show that the youngest members of each cohort are even less likely to attend university.