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Homophily, Group Size, and the Diffusion of Political Information in Social Networks: Evidence from Twitter

November 20, 2014 Comments off

Homophily, Group Size, and the Diffusion of Political Information in Social Networks: Evidence from Twitter (PDF)
Source: National Bureau of Economic Research (via University of Toronto)

In this paper, we investigate political communications in social networks characterized both by homophily–a tendency to associate with similar individuals–and group size. To generate testable hypotheses, we develop a simple theory of information diffusion in social networks with homophily and two groups: conservatives and liberals. The model predicts that, with homophily, members of the majority group have more network connections and are exposed to more information than the minority group. We also use the model to show that, with homophily and a tendency to produce like-minded information, groups are disproportionately exposed to like-minded information and the information reaches like-minded individuals more quickly than it reaches individuals of opposing ideologies. To test the hypotheses of our model, we analyze nearly 500,000 communications during the 2012 US elections in a social network of 2.2 million politically-engaged Twitter users. Consistent with the model, we find that members of the majority group in each state-level network have more connections and are exposed to more tweets than members of the minority group. Likewise, we find that groups are disproportionately exposed to like-minded information and that information reaches like-minded users more quickly than users of the opposing ideology.

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Quantifying the Lasting Harm to the U.S. Economy from the Financial Crisis

October 22, 2014 Comments off

Quantifying the Lasting Harm to the U.S. Economy from the Financial Crisis (PDF)
Source: Stanford University and NBER

The financial crisis and ensuing Great Recession left the U.S. economy in an injured state. In 2013, output was 13 percent below its trend path from 1990 through 2007. Part of this shortfall — 3.0 percentage points of real GDP — was the result of lingering slackness in the labor market in the form of abnormal unemployment and substandard weekly hours of work. The single biggest contributor was a shortfall in business capital, which accounted for 3.9 percentage points. The second largest was a shortfall of 3.5 percentage points in total factor productivity. The fourth was a shortfall of 2.4 percentage points in labor-force participation. I discuss these four sources of the injury in detail, focusing on identifying state variables that may or may not return to earlier growth paths. The conclusion is optimistic about the capital stock and slackness in the labor market and pessimistic about reversing the declines in total factor productivity and the part of the participation shortfall not associated with the weak labor market.

The Persistence and Heterogeneity of Health among Older Americans

September 4, 2014 Comments off

The Persistence and Heterogeneity of Health among Older Americans
Source: National Bureau of Economic Research

We consider how age-health profiles differ by demographic characteristics such as education, race, and ethnicity. A key feature of the analysis is the joint estimation of health and mortality to correct for the effect of mortality selection on observed age-health profiles. The model also allows for heterogeneity in individual health at a point in time and the persistence of the unobserved component of health over time. The observed component of health is based on a multidimensional index based on 27 indicators of health. Most of the key results are shown by simulations that illustrate the range of issues that can be addressed using the model. Differences in health by education and racial-ethnic group at age 50 persist throughout the remainder of life. Based on observed profiles, the health of whites is about 8 percentile points greater than the health of blacks at age 50 but by age 90 the gap is only 5 percentile points. However, when corrected for mortality selection, the health of blacks is actually declining more rapidly with age than the health of whites; the true gap widens with age. We also find that much of the difference in age-health profiles by racial-ethnic group is accounted for by differences in the levels of education between race-ethnic groups–from two-thirds to 85 percent for men and about half for women. We also simulate differences in survival probabilities by level of education and health and use these probabilities to calculate the expected present discounted value (EPDV) of an immediate annuity with first payout at age 66 for persons by gender, level of education, and health decile. The range of EPDVs is over two-fold for both men and women suggesting enormous potential for adverse selection.

Does the Gender of Offspring Affect Parental Political Orientation?

August 27, 2014 Comments off

Does the Gender of Offspring Affect Parental Political Orientation?
Source: National Bureau of Economic Research

Recently, the sex of child has been widely used as a natural experiment and shown to induce change of the allegedly stable political predisposition, however, prior results have been contradictory: in the U.K., researchers found that having daughters leads to parents favoring left-wing political parties and to holding more liberal views on family/gender roles, whereas in the U.S. scholars found that daughters were associated with more Republican (rightist) party identification and more conservative views on teen sexuality. Here, we utilize data from the General Social Survey and the European Social Survey to test the robustness of effects of offspring sex on parental political orientation while factoring out country and period differences. In analysis of 36 countries, we obtain null effects of the sex of the first child on party identification as well as on political ideology. Further, we observe no evidence of heterogeneous treatment effects. We discuss the implications of these null findings for theories of political socialization.

+ Non-paywall version (PDF)

Cash for Corollas: When Stimulus Reduces Spending

August 12, 2014 Comments off

Cash for Corollas: When Stimulus Reduces Spending
Source: National Bureau of Economic Research (via Texas A&M)

Cash for Clunkers was a 2009 economic stimulus program aimed at increasing new vehicle spending by subsidizing the replacement of older vehicles. Using a regression discontinuity design, we show the increase in sales during the two month program was completely offset during the following seven to nine months, consistent with previous research. However, we also find the program’s fuel efficiency restrictions induced households to purchase more fuel efficient but less expensive vehicles, thereby reducing industry revenues by three billion dollars over the entire nine to eleven month period. This highlights the conflict between the stimulus and environmental objectives of the policy.

The Causal Effect of Environmental Catastrophe on Long-Run Economic Growth: Evidence From 6,700 Cyclones

August 8, 2014 Comments off

The Causal Effect of Environmental Catastrophe on Long-Run Economic Growth: Evidence From 6,700 Cyclones (PDF)
Source: National Bureau of Economic Research

Does the environment have a causal effect on economic development? Using meteorological data, we reconstruct every country’s exposure to the universe of tropical cyclones during 1950-2008. We exploit random within-country year-to-year variation in cyclone strikes to identify the causal effect of environmental disasters on long-run growth. We compare each country’s growth rate to itself in the years immediately before and after exposure, accounting for the distribution of cyclones in preceding years. The data reject hypotheses that disasters stimulate growth or that short-run losses disappear following migrations or transfers of wealth. Instead, we find robust evidence that national incomes decline, relative to their pre-disaster trend, and do not recover within twenty years. Both rich and poor countries exhibit this response, with losses magnified in countries with less historical cyclone experience. Income losses arise from a small but persistent suppression of annual growth rates spread across the fifteen years following disaster, generating large and significant cumulative effects: a 90th percentile event reduces per capita incomes by 7.4% two decades later, effectively undoing 3.7 years of average development. The gradual nature of these losses render them inconspicuous to a casual observer, however simulations indicate that they have dramatic influence over the long-run development of countries that are endowed with regular or continuous exposure to disaster. Linking these results to projections of future cyclone activity, we estimate that under conservative discounting assumptions the present discounted cost of “business as usual” climate change is roughly $9.7 trillion larger than previously thought.

Decriminalizing Indoor Prostitution: Implications for Sexual Violence and Public Health

August 1, 2014 Comments off

Decriminalizing Indoor Prostitution: Implications for Sexual Violence and Public Health
Source: Social Science Research Network/National Bureau of Economic Research

Most governments in the world including the United States prohibit prostitution. Given these types of laws rarely change and are fairly uniform across regions, our knowledge about the impact of decriminalizing sex work is largely conjectural. We exploit the fact that a Rhode Island District Court judge unexpectedly decriminalized indoor prostitution in 2003 to provide the first causal estimates of the impact of decriminalization on the composition of the sex market, rape offenses, and sexually transmitted infection outcomes. Not surprisingly, we find that decriminalization increased the size of the indoor market. However, we also find that decriminalization caused both forcible rape offenses and gonorrhea incidence to decline for the overall population. Our synthetic control model finds 824 fewer reported rape offenses (31 percent decrease) and 1,035 fewer cases of female gonorrhea (39 percent decrease) from 2004 to 2009.

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