Improving the Teaching of Econometrics at Pace University Using Stata

The goal of this grant was to improve the teaching of econometrics at Pace using the computer program, Stata, the most widely-used econometrics software among applied economists

Exercise, Physical Activity, and Exertion over the Business Cycle

As economic recessions reduce employment and wages, associated shifts in time and income constraints would be expected to also impact individuals’ health behaviors. Prior work has focused exclusively on recreational exercise, which typically represents only about 4% of total daily physical exertion. The general presumption in these studies is that, because exercise improves health, if unemployment increases exercise it must also improve health. Yet a person may be laid off from a physically demanding job, exercise more, and still be less physically active than when employed. Thus the relevant question is whether unemployment leads persons to become more physically active. We study this question with the American Time Use Survey (2003-2010), exploring the impact of the business cycle (and specifically the Great Recession) on individuals’ exercise, other uses of time, and physical activity during the day. We also utilize more precise measures of exercise (and all other physical activities), which reflect information on the duration as well as intensity of each component activity, than has been employed in past studies. Using within-state variation in employment and unemployment, we find that recreational exercise tends to increase as employment decreases. In addition, we also find that individuals substitute into television watching, sleeping, childcare, and housework. However, this increase in exercise as well as other activities does not compensate for the decrease in work-related exertion due to job-loss. Thus total physical exertion, which prior studies have not analyzed, declines. These behavioral effects are strongest among low-educated males, which is validating given that the Great Recession led to some of the largest layoffs within the manufacturing, mining, and construction sectors. Due to the concentration of low-educated workers in boom-and-bust industries, the drop in total physical activity during recessions is especially problematic for vulnerable populations and may play a role in exacerbating the SES-health gradient during recessions. We also find some evidence of intra-household spillover effects, wherein individuals respond to shifts in spousal employment conditional on their own labor supply.

What climate sensitivity index is most useful for projections?

Transient climate response (TCR), transient response at 140 years (T140) and equilibrium climate sensitivity (ECS) indices are intended as benchmarks for comparing the magnitude of climate response projected by climate models. It is generally assumed that TCR or T140 would explain more variability between models than ECS for temperature change over the 21st Century, since this timescale is the realm of transient climate change. Here we find that TCR explains more variability across CMIP5 than ECS for global temperature change since pre-industrial, for 50- or 100-year global trends up to the present, and for projected change under representative concentration pathways in regions of delayed warming such as the Southern Ocean. However, unexpectedly we find that ECS correlates higher than TCR for projected change from the present in the global mean and in most regions. This higher correlation doesn’t relate to aerosol forcing, and the physical cause requires further investigation

Isolating the Effect of Major Depression on Obesity: Role of Selection Bias

There is suggestive evidence that rates of major depression have risen markedly in the U.S. concurrent with the rise in obesity. The economic burden of depression, about $100 billion annually, is under-estimated if depression has a positive causal impact on obesity. If depression plays a causal role in increasing the prevalence of obesity, then policy interventions aimed at promoting mental health may also have the indirect benefits of promoting a healthy bodyweight. However, virtually the entire existing literature on the connection between the two conditions has examined merely whether they are significantly correlated, sometimes holding constant a limited set of demographic factors. This study utilizes multiple large-scale nationally-representative datasets to assess whether, and the extent to which, the positive association reflects a causal link from major depression to higher BMI and obesity. While contemporaneous effects are considered, the study primarily focuses on the effects of past and lifetime depression to bypass reverse causality and further assess the role of non-random selection on unobservable factors. There are expectedly no significant or substantial effects of current depression on BMI or overweight/obesity, given that BMI is a stock measure that changes relatively slowly over time. Results are also not supportive of a causal interpretation among males. However, among females, estimates indicate that past or lifetime diagnosis of major depression raises the probability of being overweight or obese by about seven percentage points. Results also suggest that this effect appears to plausibly operate through shifts in food consumption and physical activity. We estimate that this higher risk of overweight and obesity among females could potentially add about 10$9.7 billion) to the estimated economic burden of depression.

Differential Impact of Recent Medicaid Expansions by Race and Ethnicity

Objective. Between 1989 and 1995, expansions in Medicaid eligibility provided publicly financed health insurance to an additional 7 million poor and near-poor children. It is not known whether these expansions affected children’s insurance coverage, use of health care services, or health status differently, depending on their race/ethnicity. The objective of this study was to examine, by race/ethnicity, the impact of the recent Medicaid expansions on levels of uninsured individuals, health care service utilization, and health status of the targeted groups of children. Methods. Using a stratified set of longitudinal data from the National Health Interview Surveys of 1989 and 1995, we compared changes in measures of health insurance coverage, health services utilization, and health status for poor white, black, and Hispanic 1- to 12-year-old children. To control for underlying trends over time, we subtracted 1989 to 1995 changes in these outcomes among nonpoor children from changes among the poor children for each race/ethnicity group. Measures of coverage included uninsured rates and Medicaid rates. Utilization measures included annual probability of visiting a doctor, annual number of doctor visits, and annual probability of hospitalization. Health status measures included self-reported health status and number of restricted-activity days in the 2 weeks before the interview. Differences in means were analyzed with the use of Student’s t tests accounting for the clustering sample design of the National Health Interview Surveys. Results. Among poor children between 1989 and 1995, uninsured rates declined by 4 percentage points for whites, 11 percentage points for blacks, and 19 percentage points for Hispanics. Medicaid rates for these groups increased by 16 percentage points, 22 percentage points, and 23 percentage points, respectively. With respect to utilization, the annual probability of seeing a physician increased 7 percentage points among poor blacks and Hispanics but only 1 percentage point among poor whites (not significant) for children in good, fair, or poor health. Among those in excellent or very good health, the respective increases were 1 percentage point for poor whites (not significant), 7 percentage points for poor blacks, and 3 percentage points for poor Hispanics (not significant). Significant increases in numbers of doctor visits per year were recorded only for poor Hispanics who were in excellent or very good health, whereas significant decreases in hospitalizations were recorded for Hispanics who were in good fair or poor health. Measures of health status remained unchanged for poor children over time. The recorded decreases in uninsured rates and increases in Medicaid coverage remained robust to adjustments for underlying trends for all 3 race/ethnicity groups. With respect to adjusted measures of utilization and health status, the only significant differences found were among poor blacks who were in good, fair, or poor health and who registered increases in the likelihood of hospitalization and in poor Hispanics who were in excellent or very good health and who registered decreases in the numbers of restricted-activity days. Conclusions. Recent expansions in the Medicaid program from 1989 to 1995 produced greater reductions in uninsured rates among poor minority children than among poor white children. Regardless of race/ethnicity, poor children did not seem to experience significant changes during the period of the expansions in either their level of health service utilization or their health status. Reproduced with permission from Pediatrics, Copyright (c) 2001 by the AAP

An observationally based constraint on the water-vapor feedback

The increase in atmospheric concentrations of water vapor with global warming is a large positive feedback in the climate system. Thus, even relatively small errors in its magnitude can lead to large uncertainties in predicting climate response to anthropogenic forcing. This study incorporates observed variability of water vapor over 2002-2009 from the Atmospheric Infrared Sounder instrument into a radiative transfer scheme to provide constraints on this feedback. We derive a short-term water vapor feedback of 2.2 ± 0.4 WmK. Based on the relationship between feedback derived over short and long timescales in twentieth century simulations of 14 climate models, we estimate a range of likely values for the long-term twentieth century water vapor feedback of 1.9 to 2.8 WmK. We use the twentieth century simulations to determine the record length necessary for the short-term feedback to approach the long-term value. In most of the climate models we analyze, the short-term feedback converges to within 15% of its long-term value after 25 years, implying that a longer observational record is necessary to accurately estimate the water vapor feedback. Key Points The water vapor feedback from observations is greater than most models predict The water vapor feedback from interannual variability is an underestimate 20 years of observations are needed to constrain the water vapor feedback

Variation in climate sensitivity and feedback parameters during the historical period

We investigate the climate feedback parameter α (W m−2 K−1) during the historical period (since 1871) in experiments using the HadGEM2 and HadCM3 atmosphere general circulation models (AGCMs) with constant preindustrial atmospheric composition and time-dependent observational sea surface temperature (SST) and sea ice boundary conditions. In both AGCMs, for the historical period as a whole, the effective climate sensitivity is ∼2 K (α≃1.7 W m−2 K−1), and α shows substantial decadal variation caused by the patterns of SST change. Both models agree with the AGCMs of the latest Coupled Model Intercomparison Project in showing a considerably smaller effective climate sensitivity of ∼1.5 K (α = 2.3 ± 0.7 W m−2 K−1), given the time-dependent changes in sea surface conditions observed during 1979–2008, than the corresponding coupled atmosphere-ocean general circulation models (AOGCMs) give under constant quadrupled CO2 concentration. These findings help to relieve the apparent contradiction between the larger values of effective climate sensitivity diagnosed from AOGCMs and the smaller values inferred from historical climate change

Adjustments in the forcing-feedback framework for understanding climate change

The traditional forcing-feedback framework has provided an indispensable basis for discussing global climate changes. However, as analysis of model behavior has become more detailed, shortcomings and ambiguities in the framework have become more evident and physical effects unaccounted for by the traditional framework have become interesting. In particular, the new concept of adjustments, which are responses to forcings that are not mediated by the global mean temperature, has emerged. This concept, related to the older ones of climate efficacy and stratospheric adjustment, is a more physical way of capturing unique responses to specific forcings. We present a pedagogical review of the adjustment concept, why it is important, and how it can be used. The concept is particularly useful for aerosols, where it helps to organize what has become a complex array of forcing mechanisms. It also helps clarify issues around cloud and hydrological response, transient vs. equilibrium climate change, and geoengineering

Human Folate Bioavailability

The vitamin folate is recognized as beneficial health-wise in the prevention of neural tube defects, anemia, cardiovascular diseases, poor cognitive performance, and some forms of cancer. However, suboptimal dietary folate intake has been reported in a number of countries. Several national health authorities have therefore introduced mandatory food fortification with synthetic folic acid, which is considered a convenient fortificant, being cost-efficient in production, more stable than natural food folate, and superior in terms of bioavailability and bioefficacy. Other countries have decided against fortification due to the ambiguous role of synthetic folic acid regarding promotion of subclinical cancers and other adverse health effects. This paper reviews recent studies on folate bioavailability after intervention with folate from food. Our conclusions were that limited folate bioavailability data are available for vegetables, fruits, cereal products, and fortified foods, and that it is difficult to evaluate the bioavailability of food folate or whether intervention with food folate improves folate status. We recommend revising the classical approach of using folic acid as a reference dose for estimating the plasma kinetics and relative bioavailability of food folate