Research

Publications:

Williams, AM., Phaneuf D., Barrett, M., Su, J.The Short Term Impact of PM2.5 on Contemporaneous Asthma Medication Use: Behavior and the Value of Pollution Reductions

Accepted, Proceedings of the National Academy of Sciences

Asthma ranks among the most costly of chronic diseases, accounting for over $50 billion annually in direct medical expenditures in the United States. At the same time, evidence has accumulated that fine particulate matter pollution can exacerbate asthma symptoms and generate substantial economic costs. To measure these costs, we use a unique nationwide panel dataset tracking asthmatic individuals’ use of rescue medication and their exposure to PM2.5 concentration between 2012 and 2017, to estimate the causal relationship between pollution and inhaler use. Our sample consists of individuals using an asthma digital health platform, which relies on a wireless sensor to track the place and time of inhaler use events, as well as regular non-event location and time indicators. These data provide an accurate measurement of inhaler use and allow spatially and temporally resolute assignment of pollution exposure. Using a high frequency research design and individual fixed effects, we find that a 1 mg/m3 (12 percent) increase in weekly exposure to PM2.5 increases weekly inhaler use by 0.82 percent. We also show that there is seasonal, regional, and income-based heterogeneity in this response. Using our response prediction, and an estimate from the literature on the willingness to pay to avoid asthma symptoms, we show that a nationwide 1 mg/m3 reduction in particulate matter concentration would generate over $350 million annually in economic benefits.

Williams, AM, Kreisel, K, Chesson, H. Impacts of Federal Prevention Funding on Reported Gonorrhea and Chlamydia Rates.

Accepted, American Journal of Preventive Medicine

Presented at the Division of STD Prevention, CDC 2017

Background: Rates of reported sexually transmitted infections (STIs) have been increasing in the United States (USA) in recent years, while public health funding has been declining. The Centers for Disease Control and Prevention (CDC) allocates annual funds to jurisdictions nationwide for STI prevention activities. The objective of this study was to assess the effectiveness of federal STI prevention funding for reducing rates of reported STIs.

Methods: We evaluated the impact of STI prevention funding (in 2016 dollars per capita) on reported chlamydia rates from 2000 to 2016 and reported gonorrhea rates from 1981 to 2016 using finite distributed lag regression models. Including lagged funding measures allowed for assessing the impact of funding over time. We also controlled for state-level socioeconomic factors, such as poverty rates, crime rates, and the age and racial makeup of the population.

Results: Results from our main model indicate that a 1% increase in annual funding would cumulatively decrease chlamydia and gonorrhea rates by 0.17% (p<0.10) and 0.33% (p<0.05), respectively. Results were similar when stratified by gender, with significant decreases in rates of reported chlamydia and gonorrhea in males of 0.33% and 0.34% (both p<0.05), and in rates of reported gonorrhea in females of 0.32% (p<0.05). The results were generally consistent across alternative model specifications and other robustness tests.

Conclusions: The significant inverse associations between federal STI prevention funding and rates of reported chlamydia and gonorrhea suggest that federally-funded STI prevention activities have a discernable effect on reducing the burden of STIs.


Williams, AM, Chesson, HW. Recent Changes in Prevention Funding to Areas with High Racial and Ethnic Disparities in Sexually Transmitted Disease Rates. Sexually Transmitted Diseases. 45(10):703-705, October 2018.


Working Papers:

Williams, AM., Phaneuf, D. The Morbidity Costs of Air Pollution: Evidence from Spending on Chronic Respiratory Conditions

Under Review

Presented at the 2016 AERE Summer Conference, UW Madison AAE 2017, Environmental Defense Fund 2017

Medical expenditures on respiratory ailments such as asthma and chronic obstructive pulmonary disease (COPD) exceed $75 billion annually in the US, and research demonstrates that exposure to air pollution can exacerbate symptoms from these diseases. How much of this spending is attributable to air pollution, and what are the welfare consequences of pollution-induced changes in expenditures? Despite the enormous scale of spending on respiratory diseases, there is little research in economics examining these questions related to morbidity. In this paper, we link household level data from the Medical Expenditure Panel Survey (MEPS) to concentrations of particulate matter across 23 US metropolitan areas for the years 1999 to 2003. Using an extensive set of fixed effects and an instrumental variables strategy, we find that a standard deviation increase in fine particulate matter increases spending on asthma and COPD by 12.7 percent. Our theoretical framing implies a lower bound willingness to pay for a reduction of this size of that exceeds $9 billion annually.


Williams, AM. Using Residential Sorting Behavior to Better Understand the Relationship between Urban Greenspace and Health

Presented at the 2017 ASSA meetings in Chicago.

This paper examines the relationship between neighborhood amenities, such as parks or open space, and health. I focus on an important empirical issue in this literature: people sort themselves into neighborhoods based on the characteristics of those neighborhoods and their personal preferences. I use restricted access data from the National Longitudinal Study of Adolescent to Adult Health (Add Health) to model the relationship between urban greenspace and health. In particular, I use knowledge of residential sorting behavior to construct novel instruments for neighborhood amenity levels in order to address a standard endogeneity problem. My findings show that time-variant unobserved variables bias downward the estimated effect of access to greenspace on health. This implies that simply adding fixed effects in a panel setting may not be sufficient for identification.


Williams, AM. Who Bears the Unseen Costs of Pollution? Understanding the Determinants of Defensive Behavior

Under Review

I use individual level data from the 2007-2010 National Health and Nutrition Examination Survey, which asks participants if they engaged in avoidance behavior (an action taken to reduce exposure to pollution) in the previous year, and, if so, which types of behaviors. I estimate how individual characteristics, such as being asthmatic, insurance status, education, and income, impact the decision to engage in avoidance behaviors. I merge additional variables including local weather and pollution measures using restricted geographic data through a Census Federal Statistical Research Data Center. This allows me to control for important covariates and use instrumental variable regressions to account for endogeneity. I find that educated and asthmatic individuals are more likely to engage in avoidance behaviors in response to air quality alerts, while those with stronger preferences for outdoor recreation are less likely to respond. This highlights a tradeoff between values for leisure time and health on high air pollution days, and it provides a more nuanced characterization of who engages in avoidance behaviors and why.


McCree, DH, Williams, AM, Chesson HW, Beer, L, Jeffries, WL, Lemon, A, Prather, C, Sutton, M, McCray, E. Changes in Disparities in Estimated HIV Incidence Rates among Black, Hispanic/Latino and White Men Who Have Sex with Men (MSM) in the United States, 2010-2015.

Under Review, JAIDS