Olivier Deschenes

Status and solutions for the world's unassessed fisheries.

First, Find Fish While salmon, cod, and tuna fisheries are regularly monitored and assessed, this is not the case for about 80% of the fish species harvested throughout the world. Costello et al. (p. 517 published online 27 September; see the Perspective by Pikitch) used a model that integrates harvest, population, and ecological data to estimate the status of unassessed fisheries, based on ecologically analogous, regularly assessed fisheries. Generally, unassessed fisheries are in worse condition with declining fish stocks compared with regularly assessed fisheries. Poorly monitored, small-size fisheries are in decline, but few of them are near collapse. Recent reports suggest that many well-assessed fisheries in developed countries are moving toward sustainability. We examined whether the same conclusion holds for fisheries lacking formal assessment, which comprise >80% of global catch. We developed a method using species’ life-history, catch, and fishery development data to estimate the status of thousands of unassessed fisheries worldwide. We found that small unassessed fisheries are in substantially worse condition than assessed fisheries, but that large unassessed fisheries may be performing nearly as well as their assessed counterparts. Both small and large stocks, however, continue to decline; 64% of unassessed stocks could provide increased sustainable harvest if rebuilt. Our results suggest that global fishery recovery would simultaneously create increases in abundance (56%) and fishery yields (8 to 40%).

Extreme Weather Events, Mortality and Migration

We estimate the effect of extreme weather on life expectancy in the United States. Using high-frequency data, we find that both extreme heat and cold result in immediate increases in mortality. The increase in mortality following extreme heat appears mostly driven by near-term displacement, while the increase in mortality following extreme cold is long lasting. We estimate that the number of annual deaths attributable to cold temperature is 0.8 of average annual deaths in our sample. The longevity gains associated with mobility from the Northeast to the Southwest account for 4 to 7 of the total gains in life expectancy experienced by the U.S. population over the past thirty years.

The Long-Term Impact of Military Service on Health: Evidence from World War II and Korean War Veterans

During the World War II and Korean War era, the U.S. military freely distributed cigarettes to overseas personnel and provided low-cost tobacco products on domestic military bases. In fact, even today the military continues to sell subsidized tobacco products on its bases. Using a variety of instrumental variables approaches to deal with nonrandom selection into the military and into smoking, we provide substantial evidence that cohorts with higher military participation rates subsequently suffered more premature mortality. More importantly, we show that a large fraction, 35 to 79 percent, of the excess veteran deaths due to heart disease and lung cancer are attributable to military-induced smoking.

Sex Preferences, Marital Dissolution, and the Economic Status of Women

The rise in the divorce rate over the past 40 years is one of the fundamental changes in American society. A substantial number of women and children now spend some fraction of their life in single female-headed households, leading many to be concerned about their economic circumstances. Estimating the cause-to-effect relationship between marital dissolution and female economic status is complicated because the same factors that increase marital instability also may affect the economic status and labor market outcomes of women. We propose an instrumental variables solution to this problem based on the sex of the firstborn child. This strategy exploits the fact that the sex of the firstborn child is random and the fact that marriages are less likely to continue following the birth of girls as opposed to boys. Our IV results cast doubt on the widely held view that divorce causes large declines in economic status for women. Once the negative selection into divorce is accounted for, our results show that, on average, ever-divorced women live in households with more income per person than never-divorced women.

Defensive Investments and the Demand for Air Quality: Evidence from the Nox Budget Program and Ozone Reductions

The demand for air quality depends on health impacts and defensive investments that improve health, but little research assesses the empirical importance of defenses. We study the NOx Budget Program (NBP), an important cap-and-trade market for nitrogen oxides (NOx) emissions, a key ingredient in ozone air pollution. A rich quasi-experiment suggests that the NBP decreased NOx emissions, ambient ozone concentrations, pharmaceutical expenditures, and mortality rates. Reductions in pharmaceutical purchases and mortality are valued at about

Estimating the Effects of Family Background on the Return to Schooling

800 million and

Maybe Next Month? Temperature Shocks, Climate Change, and Dynamic Adjustments in Birth Rates

1.5 billion annually, respectively, in a region covering 19 Eastern and Midwestern United States; these findings suggest that defensive investments account for more than one-third of the willingness-to-pay for reductions in NOx emissions. Further, the NBP’s estimated benefits easily exceed its costs and instrumental variable estimates indicate that the estimated benefits of NOx reductions are substantial.

Spatiotemporal variation in the relationship between landscape simplification and insecticide use

This article examines the causal link between family background characteristics—parental education and family size—and returns to schooling. I implement a model of schooling and earnings with heterogeneous returns to education using data from the Occupational Change in a Generation Survey. I find that men raised in larger families have substantially lower returns to education, whereas the combined effects of parental education are more modest. In addition, like other “supply-side” instrumental variables studies of the causal effect of education, I find two-stage least squares estimates that are larger than the corresponding ordinary least squares estimates. The results suggest an alternative explanation for this phenomenon: constant marginal return to schooling, combined with a negative absolute ability bias and a positive comparative advantage bias.

Agricultural pesticide use and adverse birth outcomes in the San Joaquin Valley of California

Dynamic adjustments could be a useful strategy for mitigating the costs of acute environmental shocks when timing is not a strictly binding constraint. To investigate whether such adjustments could apply to fertility, we estimate the effects of temperature shocks on birth rates in the United States between 1931 and 2010. Our innovative approach allows for presumably random variation in the distribution of daily temperatures to affect birth rates up to 24 months into the future. We find that additional days above 80 °F cause a large decline in birth rates approximately 8 to 10 months later. The initial decline is followed by a partial rebound in births over the next few months implying that populations can mitigate the fertility cost of temperature shocks by shifting conception month. This dynamic adjustment helps explain the observed decline in birth rates during the spring and subsequent increase during the summer. The lack of a full rebound suggests that increased temperatures due to climate change may reduce population growth rates in the coming century. As an added cost, climate change will shift even more births to the summer months when third trimester exposure to dangerously high temperatures increases. Based on our analysis of historical changes in the temperature-fertility relationship, we conclude air conditioning could be used to substantially offset the fertility costs of climate change.

Children and Climate Change: Introducing the Issue

Agrochemicals have numerous negative impacts on human health, ecosystem services, and ecological communities. Thus, their efficient use is an economic and ecological priority. Simplified landscapes may enhance insecticide use by reducing natural enemies and increasing connectivity of crops, but empirical tests of this theory are inconclusive. We explored the relationship between landscape simplification and insecticide use using longitudinal data from USDA Census of Agriculture spanning six censuses and 25 years (1987, 1992, 1997, 2002, 2007, 2012) for nearly 3000 counties across the continental United States. The effect of landscape simplification was highly variable spatially and temporally. Landscape simplification was consistently correlated with increased insecticide use in some regions, but not in others. Our results indicate that the landscape-simplification-insecticide-use relationship is dynamic, and that national land use policy would benefit from actions that adequately reflect the spatial differences in the importance of landscape complexity to insecticide use.