Knowledge that Transforms

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The “Out of Africa” Hypothesis, Human Genetic Diversity, and Comparative Economic Development

American Economic Review 2013 103(1), 1-46 open access
This research argues that deep-rooted factors, determined tens of thousands of years ago, had a significant effect on the course of economic development from the dawn of human civilization to the contemporary era. It advances and empirically establishes the hypothesis that, in the course of the exodus of Homo sapiens out of Africa, variation in migratory distance from the cradle of humankind to various settlements across the globe affected genetic diversity and has had a long-lasting effect on the pattern of comparative economic development that is not captured by geographical, institutional, and cultural factors. In particular, the level of genetic diversity within a society is found to have a hump-shaped effect on development outcomes in both the pre-colonial and the modern era, reflecting the trade-off between the beneficial and the detrimental effects of diversity on productivity. While the intermediate level of genetic diversity prevalent among Asian and European populations has been conducive for development, the high degree of diversity among African populations and the low degree of diversity among Native American populations have been a detrimental force in the development of these regions.

Boys' Cognitive Skill Formation and Physical Growth: Long-Term Experimental Evidence on Critical Ages for Early Childhood Interventions

American Economic Review 2013 103(3), 467-471
It is often assumed that early life circumstances, in particular before age two, are important for later human capital development. Using experimental variation in the timing of benefits from a conditional cash transfer program, we test the hypothesis that intervention starting in utero and continuing in the first two years is critical. At age ten, boys exposed to the program during this period had better cognitive, but not anthropometric, outcomes than those exposed in their second year of life or later. The lack of a differential effect on anthropometrics was due catch-up growth.

Some Basic Economics of National Security

American Economic Review 2013 103(3), 508-511
We define national security (NS) as public policies that protect the safety or welfare of a nation's citizens from substantial threats. NS capital provides societal insurance against widespread harm or catastrophe, so optimal NS investments may have very low expected rates of return. Investment targeted at extreme events (war) has spillovers, reducing potential harm in less threatening situations as well. Potential threats are highly uncertain, which raises the value of ex-post scalability of NS technologies. Higher probabilities of extreme events raise the demand for flexibility, so ex-post responses to threats are more elastic, but may reduce current precaution.

Are Government Spending Multipliers Greater during Periods of Slack? Evidence from Twentieth-Century Historical Data

American Economic Review 2013 103(3), 129-134
A key question that has arisen during recent debates is whether government spending multipliers are larger during times when resources are idle. This paper seeks to shed light on this question by analyzing new quarterly historical data covering multiple large wars and depressions in the United States and Canada. Using Jorda's (2005) method for estimating impulse responses, we find no evidence that multipliers are greater during periods of high unemployment in the United States. In every case, they are below unity. We do find evidence of higher multipliers during periods of slack in Canada, with some multipliers above unity.

Output Spillovers from Fiscal Policy

American Economic Review 2013 103(3), 141-146
For a large number of OECD countries we estimate the cross-country spillover effects of government purchases on output. Following the methodology in Auerbach and Gorodnichenko (2012a, b), we allow these multipliers to vary smoothly according to the state of the economy and use real-time forecast data to purge policy innovations of their predictable components. Our findings suggest that cross-country spillovers have an important impact. The findings also confirm those of our earlier papers--namely that fiscal shocks have a larger impact when the affected country is in recession.

Deconstructing Income and Income Inequality Measures: A Crosswalk from Market Income to Comprehensive Income

American Economic Review 2013 103(3), 173-177
Recent research on levels and trends in the United States in income inequality vary substantially in how they measure income. We show the sensitivity of alternative income measures in capturing income trends using a unified data set. Focusing solely on market income or including realized taxable capital gains based on IRS tax return data in more comprehensive household income measures will dramatically increase inequality growth compared to capital gains measures more in keeping with Haig-Simons principles. Using a measure of yearly accrued capital gains dramatically reduces observed growth in income inequality across the distribution, but also equalizes income growth since 1989.

Immigration, Offshoring, and American Jobs

American Economic Review 2013 103(5), 1925-1959 open access
Following Grossman and Rossi-Hansberg (2008) we present a model in which tasks of varying complexity are matched to workers of varying skill in order to develop and test predictions regarding the effects of immigration and offshoring on US native-born workers. We find that immigrant and native-born workers do not compete much due to the fact that they tend to perform tasks at opposite ends of the task complexity spectrum, with offshore workers performing the tasks in the middle. An effect of offshoring and a positive effect of immigration on native-born employment suggest that immigration and offshoring improve industry efficiency. (JEL J24, J41, J61, L24)

Immigration and Employer Transitions for STEM Workers

American Economic Review 2013 103(3), 193-197 open access
The firm is almost entirely absent from models of immigration, and yet firms play a central role for high-skilled immigration. The H-1B visa program, for example, is a firm-sponsored entry where firms are responsible for every stage: from identifying the immigrant, to employing them, to filing for permanent residency on behalf of the immigrant. This central role of firms for high-skilled immigration suggests the traditional lens for evaluating the impact of immigration on natives through local area labor markets or national age-education approaches may miss important dynamics. We analyze the employment and wage trajectories of high-skilled workers born in America when a high-skilled immigrant arrives at their work site. We use linked employer-employee data during the 1995-2008 period from the Census Bureau for this exercise, which identifies the immigration status and country-of-birth of workers. We follow the subsequent career path of workers after high-skilled immigration occurs to the employee's work site both within firms (e.g., changes in employee salary, relocation to other sites) and across firms (e.g., movements to new jobs or out of workforce, long-term salary adjustments). The richness and depth of the Census Bureau data allow for multiple comparison points: selection on observables (e.g., age, tenure, salary levels and recent growth), varying immigration treatments across different work sites for the same firm for otherwise comparable employees, and (for a subset of cases and short time period at the end of our sample) randomization in H-1B admission lotteries.

Comparisons of Weekly Hours over the Past Century and the Importance of Work-Sharing Policies in the 1930s

American Economic Review 2013 103(3), 105-110
Changes in the work week drove a larger portion of changes in total labor input during the Great Depression of the 1930s than during other decades. Work-sharing policies appear to be responsible. Herbert Hoover created various work-sharing committees--led by key industrialists--which pushed for shorter work weeks. And Franklin Roosevelt's President's Reemployment Agreement called for sharp cuts in weekly work hours. Spreading available work amongst more people was the goal. During these periods between 50 and 90 percent of declines in labor input were accommodated by falling hours. In recent decades employers have instead relied on layoffs to achieve the same end.

Natural Gas: From Shortages to Abundance in the United States

American Economic Review 2013 103(3), 338-343
The history of natural gas wellhead and pipeline regulation, deregulation and regulatory reforms are discussed. These reforms brought natural gas shortages and pipeline inefficiencies to an end. They also created an economic platform that could support unanticipated developments in the supply and costs of domestic natural gas. Such unanticipated developments emerged in the last few years as several technological innovations came together to make it commercially attractive to development US shale gas deposits located deep in the earth. How and why shale gas supplies will lead to dramatic changes in the United States' energy future with appropriate environmental regulatory reforms are discussed.