Knowledge that Transforms

We present and discuss preliminary evidence suggesting that credit ratings significantly influenced prices for subprime mortgage-backed securities issued in the period leading up to the recent financial crisis. Ratings are closely correlated with prices even controlling for a rich set of security- and loan-level controls. This incremental variation in ratings has much less predictive power for security defaults, however, based on findings to date from our ongoing research, suggesting prices were excessively sensitive to ratings relative to their informational content.

In the sixteenth century, North America contained 25 to 30 million buffalo; by the late nineteenth century fewer than 100 remained. While removing the buffalo east of the Mississippi took over 100 years, the remaining 10 to 15 million buffalo on the Great Plains were killed in a punctuated slaughter lasting little more than ten years. I employ theory, international trade statistics, and first-person accounts to argue the slaughter was initiated by a foreign-made innovation and fueled by a foreign demand for industrial leather. European demand and American policy failure are jointly responsible for the “Slaughter on the Plains.”

In the last 15 years, economists and economic historians have argued that Africa has undergone a “reversal of fortune” and that ethnic fragmentation is a significant cause of Africa's underdevelopment. In this article, we join these narratives by arguing that the transatlantic slave trade increased the degree of ethnic heterogeneity in Africa today. Using both correlational and causal instrumental variables analysis, we find an economically and statistically significant positive relationship between slave exports and ethnic heterogeneity. This relationship is robust to changes in the scheme for drawing ethnic boundaries and the choice of observational unit.

We investigate the effect of house price changes on divorce using data for 1991–2010 from the Current Population Survey and the Federal Housing Finance Agency. Our findings suggest that changing house prices significantly affect the share of a cohort that is divorced, and that these effects are asymmetric with respect to housing gains versus losses. In addition, we find differential effects for groups that are more likely to be homeowners versus renters. Some of this evidence is consistent with homeowners being locked into their homes—and hence marriages—by increased transactions costs in down markets.

The lead article in the inaugural issue of the AER examines the common property resource problem as applied to water in the Western United States.

The consumption growth beta of an investment strategy that goes long in high interest rate currencies and short in low interest rate currencies is large and significant. Consumption risk price differs significantly from zero, even after accounting for the sampling uncertainty introduced by the estimation of the consumption betas. The constant in the regression of average returns on consumption betas is not significant. Additionally, this investment strategy's consumption and market betas increase during recessions and times of crisis, when risk prices are high, implying that the unconditional betas understate its riskiness. JEL: C58, E21, F31, G11, G12

This paper uses newly available data on plant level regulatory status linked to the Census Longitudinal Business Database to measure the impact of changes in county level environmental regulations on plant and sector employment levels. Estimates from a variety of specifications suggest a strong connection between changes in environmental regulatory stringency and both employment growth and levels in the affected sectors. The preferred estimates suggest that changes in county level regulatory status due to the 1990 Clean Air Act Amendments reduced the size of the regulated sector by as much as 15 percent in the 10 years following the changes.

Under its health reform legislation, Massachusetts has achieved near universal insurance coverage, along with significant gains in health care access and affordability. This paper examines the impacts of health reform in Massachusetts on differences in coverage, access, and affordability for women and men. We find that both women and men gained under health reform, with the gender gap in insurance coverage narrowed as men's coverage increased relative to that of women. However, the gaps in access and affordability of care have not narrowed—women in Massachusetts continue to report more unmet need for care and problems affording care than men.

Medicare Part D relies upon drug plan competition. Plans have enormous scope to design benefits and to set premiums, but they may not charge differential premiums based on risk. We use the formulary and benefit design of all Medicare prescription drug plans and pharmacy claims data to construct a simulation model of out-of-pocket drug spending. We use this simulation model to examine individual incentives in Medicare Part D for adverse selection. We find that high drug users have much stronger incentives to enroll in generous plans than do low users, thus there is significant scope for adverse selection.

Existing indicators of technical change are plagued by shortcomings. I present new measures based on books published in the field of technology that resolve many of these problems and use them to identify the impact of technology shocks on economic activity. They are positively linked to changes in R&D and scientific knowledge, and capture the new technologies' commercialization dates. Changes in information technology are found to be important sources of economic fluctuations in the post-WWII period, and total factor productivity, investment, and, to a lesser extent, labor are all shown to increase following a positive technology shock.