That hurts

Kevin Lewis

February 13, 2018

Give me 3': Do minimum distance passing laws reduce bicyclist fatalities?
Cody Nehiba
Economics of Transportation, forthcoming


Safely integrating bicyclists onto roadways in the United States has become an important issue as the number of cyclists has steadily increased in recent decades. These concerns have led many city and state legislatures to pass laws requiring drivers to provide a minimum amount of distance between their vehicle and cyclists when passing them on roadways. Many believe these laws are ineffective in reducing the number of bicyclist fatalities because they are difficult for police to enforce, contain loopholes, and the minimum distance required is inadequate. This paper tests this claim empirically using data on 18,534 bicyclist fatalities from the Fatality Analysis Reporting System and a differences-in-differences approach, in a negative binomial model, to identify the effect of minimum distance passing laws on bicyclist fatalities. The analysis fails to find a significant effect of enacting a minimum distance passing law on the number of cyclist fatalities after controlling for differences in weather, demographics, bicycling commuter rates, state level traffic, and time variation.

Go Big or Go Home: Partially-Effective Vaccines Can Make Everyone Worse Off
Eduard Talamàs & Rakesh Vohra
University of Pennsylvania Working Paper, January 2018


Vaccines are crucial to curb infectious-disease epidemics. Indeed, one of the highest priorities of the National Institutes of Health (NIH) on the HIV front is the development and delivery of a vaccine that is at least moderately effective. However, risk compensation could undermine the ability of partially-effective vaccines to curb epidemics: Since vaccines reduce the cost of risky interactions, vaccinated agents may optimally choose to engage in more of them and, as a result, may increase everyone’s infection probability. We show that — in contrast to the prediction of standard models — things can be worse than that: A free but only partially effective vaccine can reduce everyone’s welfare. The reason is simple: By reducing the cost of risky interactions, a partially-effective vaccine can destabilize the existing interaction structure in favor of a less efficient one. Because of the strategic complementarities in risky interactions that we show arise when agents strategically choose their partners, the most efficient stable interaction structure after the introduction of a partially-effective vaccine can be much denser and — due to the negative externalities of risky interactions — worse for everyone. The result of this paper underscores the importance of taking into account the effects that different interventions have on social structure, and it suggests that the NIH might want to go big — i.e. deliver a highly-effective vaccine — or go home.

Delays in Global Disease Outbreak Responses: Lessons from H1N1, Ebola, and Zika
Steven Hoffman & Sarah Silverberg
American Journal of Public Health, March 2018, Pages 329-333


In global disease outbreaks, there are significant time delays between the source of an outbreak and collective action. Some delay is necessary, but recent delays have been extended by insufficient surveillance capacity and time-consuming efforts to mobilize action. Three public health emergencies of international concern (PHEICs) — H1N1, Ebola, and Zika — allow us to identify and compare sources of delays and consider seven hypotheses about what influences the length of delays. These hypotheses can then motivate further research that empirically tests them. The three PHEICs suggest that deferred global mobilization is a greater source of delay than is poor surveillance capacity. These case study outbreaks support hypotheses that we see quicker responses for novel diseases when outbreaks do not coincide with holidays and when US citizens are infected. They do not support hypotheses that we see quicker responses for more severe outbreaks or those that threaten larger numbers of people. Better understanding the reason for delays can help target policy interventions and identify the kind of global institutional changes needed to reduce the spread and severity of future PHEICs.

Far-UVC light: A new tool to control the spread of airborne-mediated microbial diseases
David Welch et al.
Scientific Reports, February 2018


Airborne-mediated microbial diseases such as influenza and tuberculosis represent major public health challenges. A direct approach to prevent airborne transmission is inactivation of airborne pathogens, and the airborne antimicrobial potential of UVC ultraviolet light has long been established; however, its widespread use in public settings is limited because conventional UVC light sources are both carcinogenic and cataractogenic. By contrast, we have previously shown that far-UVC light (207–222 nm) efficiently inactivates bacteria without harm to exposed mammalian skin. This is because, due to its strong absorbance in biological materials, far-UVC light cannot penetrate even the outer (non living) layers of human skin or eye; however, because bacteria and viruses are of micrometer or smaller dimensions, far-UVC can penetrate and inactivate them. We show for the first time that far-UVC efficiently inactivates airborne aerosolized viruses, with a very low dose of 2 mJ/cm2 of 222-nm light inactivating >95% of aerosolized H1N1 influenza virus. Continuous very low dose-rate far-UVC light in indoor public locations is a promising, safe and inexpensive tool to reduce the spread of airborne-mediated microbial diseases.

Association of Exposure to Communities With Higher Ratios of Obesity with Increased Body Mass Index and Risk of Overweight and Obesity Among Parents and Children
Ashlesha Datar & Nancy Nicosia
JAMA Pediatrics, forthcoming

Design, Setting, and Participants: This natural experiment study used the routine assignment of military service members to installations as a source of exogenous variation in exposure to communities with higher vs lower rates of obesity. The study, which used data collected by the Military Teenagers' Environments, Exercise, and Nutrition Study, examined families from 38 military installations around the United States to determine if individuals had higher BMI and greater odds of overweight and obesity when assigned to installations in counties with higher rates of obesity. The study also examined if the relationship persisted after controlling for shared built environments. The participants included 1 parent and 1 child aged 12 or 13 years from 1519 families of Army-enlisted personnel. Data analysis was completed from November 2016 to October 2017.

Results: Members of 1519 families participated, including 1314 adults (of whom 740, or 56%, were fathers) and 1111 children (of whom 576, or 52%, were boys); anthropometric measurements were performed on 458 children. The sample was 40% white, 22% black, 24% Hispanic, and 14% other races/ethnicities. A 1 percentage point higher county obesity rate was associated with a higher BMI (a difference of 0.08; 95% CI, 0.02-0.13) and greater odds of obesity (adjusted odds ratio [aOR], 1.05; 95% CI, 1.02-1.08) in parents, and a higher BMI z score (0.01; 95% CI, 0.003-0.02) and greater odds of overweight/obesity (aOR, 1.04; 95% CI, 1.01-1.06) in children. The evidence supported stronger associations among families with more time at installation and off-installation residence. Associations persisted even after controlling for shared built environments.

The slowing pace of life expectancy gains since 1950
Carolina Cardona & David Bishai
BMC Public Health, January 2018

Background: New technological breakthroughs in biomedicine should have made it easier for countries to improve life expectancy at birth (LEB). This paper measures the pace of improvement in the decadal gains of LEB, for the last 60-years adjusting for each country’s starting point of LEB.

Methods: LEB increases over the next 10-years for 139 countries between 1950 and 2009 were regressed on LEB, GDP, total fertility rate, population density, CO2 emissions, and HIV prevalence using country-specific fixed effects and time-dummies. Analysis grouped countries into one-of-four strata: LEB < 51, 51 ≤ LEB < 61, 61 ≤ LEB < 71, and LEB ≥ 71.

Results: The rate of increase of LEB has fallen consistently since 1950 across all strata. Results hold in unadjusted analysis and in the regression-adjusted analysis. LEB decadal gains fell from 4.80 (IQR: 2.98–6.20) years in the 1950s to 2.39 (IQR:1.80–2.80) years in the 2000s for the healthiest countries (LEB ≥ 71). For countries with the lowest LEB (LEB < 51), decadal gains fell from 7.38 (IQR:4.83–9.25) years in the 1950s to negative 6.82 (IQR: -12.95--1.05) years in the 2000s. Multivariate analysis controlling for HIV prevalence, GDP, and other covariates shows a negative effect of time on LEB decadal gains among all strata.

Health and health inequality during the Great Recession: Evidence from the PSID
Huixia Wang, Chenggang Wang & Timothy Halliday
Economics & Human Biology, May 2018, Pages 17–30


We estimate the impact of the Great Recession of 2007–2009 on health outcomes in the United States. We show that a one percentage point increase in the unemployment rate resulted in a 7.8–8.8% increase in reports of poor health. In addition, mental health was adversely impacted. These effects were concentrated among those with strong labor force attachments. Whites, the less educated, and women were the most impacted demographic groups.

Impact of Volunteering on Cognitive Decline of the Elderly
Sumedha Gupta
Journal of the Economics of Ageing, November 2018, Pages 46–60


Cognitive decline among the elderly imposes a large welfare and health care cost on the individual as well as society. Little however is known about factors that can mitigate cognitive decline. Using seven waves of the Health and Retirement Study and a fixed effects - instrumental variable methodology, this study estimates the effects of volunteering on old age cognitive decline. Although cognitive decline is an inevitable aspect of aging, our results suggest that volunteering participation significantly forestalls its progress among individuals aged 60 years and older.

Economic Freedom and Exercise: Evidence from State Outcomes
Joshua Hall, Brad Humphreys & Jane Ruseski
Southern Economic Journal, forthcoming


Exercise is an important part of a healthy lifestyle and influences a variety of health outcomes. Regions vary in their levels of exercise due to geography, climate, culture, and policy. The extent to which a country's policies are consistent with economic freedom has been found to be positively associated with greater participation in physical activity. We empirically investigate the relationship between economic freedom and exercise across U.S. states. Contrary to the cross-country results, we find that states with higher levels of economic freedom have lower rates of participation in exercise.

Child Mortality In The US And 19 OECD Comparator Nations: A 50-Year Time-Trend Analysis
Ashish Thakrar et al.
Health Affairs, January 2018, Pages 140-149


The United States has poorer child health outcomes than other wealthy nations despite greater per capita spending on health care for children. To better understand this phenomenon, we examined mortality trends for the US and nineteen comparator nations in the Organization for Economic Cooperation and Development for children ages 0–19 from 1961 to 2010 using publicly available data. While child mortality progressively declined across all countries, mortality in the US has been higher than in peer nations since the 1980s. From 2001 to 2010 the risk of death in the US was 76 percent greater for infants and 57 percent greater for children ages 1–19. During this decade, children ages 15–19 were eighty-two times more likely to die from gun homicide in the US. Over the fifty-year study period, the lagging US performance amounted to over 600,000 excess deaths. Policy interventions should focus on infants and on children ages 15–19, the two age groups with the greatest disparities, by addressing perinatal causes of death, automobile accidents, and assaults by firearm.

The role of obesity in exceptionally slow US mortality improvement
Samuel Preston, Yana Vierboom & Andrew Stokes
Proceedings of the National Academy of Sciences, 30 January 2018, Pages 957-961


Recent studies have described a reduction in the rate of improvement in American mortality. The pace of improvement is also slow by international standards. This paper attempts to identify the extent to which rising body mass index (BMI) is responsible for reductions in the rate of mortality improvement in the United States. The data for this study were obtained from subsequent cohorts of the National Health and Nutrition Examination Survey (NHANES III, 1988–1994; NHANES continuous, 1999–2010) and from the NHANES linked mortality files, which include follow-up into death records through December 2011. The role of BMI was estimated using Cox models comparing mortality trends in the presence and absence of adjustment for maximum lifetime BMI (Max BMI). Introducing Max BMI into a Cox model controlling for age and sex raised the annual rate of mortality decline by 0.54% (95% confidence interval 0.45–0.64%). Results were robust to the inclusion of other variables in the model, to differences in how Max BMI was measured, and to how trends were evaluated. The effect of rising Max BMI is large relative to international mortality trends and to alternative mortality futures simulated by the Social Security Administration. The increase in Max BMI over the period 1988–2011 is estimated to have reduced life expectancy at age 40 by 0.9 years in 2011 (95% confidence interval 0.7–1.1 years) and accounted for 186,000 excess deaths that year. Rising levels of BMI have prevented the United States from enjoying the full benefits of factors working to improve mortality.

Sleep Duration in the United States 2003-2016: First Signs of Success in the Fight Against Sleep Deficiency?
Mathias Basner & David Dinges
Sleep, forthcoming

Methods: The American Time Use Survey (ATUS), representative of US residents ≥15 years, was used to investigate trends in self-reported sleep duration and waking activities for the period 2003-2016 (N=181,335 respondents).

Results: Sleep duration increased across survey years both on weekdays (+1.40 min/year) and weekends (+0.83 min/year, both p<0.0001, adjusted models). This trend was observed in students, employed respondents, and retirees, but not in those unemployed or not in the labor force. On workdays, the prevalence of short (≤7h), average (>7-9h), and long (>9h) sleep changed by -0.44%/year (p<0.0001), -0.03%/year (p=0.5515), and +0.48%/year (p<0.0001), respectively. The change in sleep duration was predominantly explained by respondents retiring earlier in the evening. The percentage of respondents who watched TV or read before bed – two prominent waking activities competing with sleep – decreased over the same time period, suggesting that portions of the population are increasingly willing to trade time in leisure activities for more sleep. The results also suggest that increasing online opportunities to work, learn, bank, shop, and perform administrative tasks from home freed up time that likely contributed to increased sleep duration.

Is “Delitigation” Associated with a Change in Product Safety? The Case of Vaccines
Gayle DeLong
Review of Industrial Organization, February 2018, Pages 1–53


This study investigates whether the threat of litigation induces firms to provide safer products in a regulated industry. I analyze whether removing litigation risk or “delitigation” of product liability is associated with a change in the safety of vaccines. Using U.S. nationwide and state-level data, I find that vaccines that were licensed after legislation that preempted most product liability lawsuits are associated with a significantly higher incidence of adverse events than were vaccines that were licensed under a previous regime that permitted consumers to sue. Oaxaca decomposition suggests that the difference is due to the policy change. The results suggest that product safety deteriorates when consumers are no longer able to sue manufacturers.

The Impact of Health on Labor Market Outcomes: Experimental Evidence from MRFIT
Melvin Stephens & Desmond Toohey
NBER Working Paper, January 2018


While economists have posited that health investments increase earnings, isolating the causal effect of health is challenging due both to reverse causality and unobserved heterogeneity. We examine the labor market effects of a randomized controlled trial, the Multiple Risk Factor Intervention Trial (MRFIT), which monitored nearly 13,000 men for over six years. We find that this intervention, which provided a bundle of treatments to reduce coronary heart disease mortality, increased earnings and family income. We find few differences in estimated gains by baseline health and occupation characteristics. Reductions in serious illnesses and work-limiting disabilities likely contributed to the observed gains.

Association of Race and Ethnicity With Live Donor Kidney Transplantation in the United States From 1995 to 2014
Tanjala Purnell et al.
Journal of the American Medical Association, 2 January 2018, Pages 49-61

Design, Setting, and Participants: A secondary analysis of a prospectively maintained cohort study conducted in the United States of 453 162 adult first-time kidney transplantation candidates included in the Scientific Registry of Transplant Recipients between January 1, 1995, and December 31, 2014, with follow-up through December 31, 2016.

Results: Among 453 162 adult kidney transplantation candidates (mean [SD] age, 50.9 [13.1] years; 39% were women; 48% were white; 30%, black; 16%, Hispanic; and 6%, Asian), 59 516 (13.1%) received LDKT. Overall, there were 39 509 LDKTs among white patients, 8926 among black patients, 8357 among Hispanic patients, and 2724 among Asian patients. In 1995, the cumulative incidence of LDKT at 2 years after appearing on the waiting list was 7.0% among white patients, 3.4% among black patients, 6.8% among Hispanic patients, and 5.1% among Asian patients. In 2014, the cumulative incidence of LDKT was 11.4% among white patients, 2.9% among black patients, 5.9% among Hispanic patients, and 5.6% among Asian patients. From 1995-1999 to 2010-2014, racial/ethnic disparities in the receipt of LDKT increased (P < .001 for all statistical interaction terms in adjusted models comparing white patients vs black, Hispanic, and Asian patients). In 1995-1999, compared with receipt of LDKT among white patients, the adjusted subhazard ratio was 0.45 (95% CI, 0.42-0.48) among black patients, 0.83 (95% CI, 0.77-0.88) among Hispanic patients, and 0.56 (95% CI, 0.50-0.63) among Asian patients. In 2010-2014, compared with receipt of LDKT among white patients, the adjusted subhazard ratio was 0.27 (95% CI, 0.26-0.28) among black patients, 0.52 (95% CI, 0.50-0.54) among Hispanic patients, and 0.42 (95% CI, 0.39-0.45) among Asian patients.

Conclusions and Relevance: Among adult first-time kidney transplantation candidates in the United States who were added to the deceased donor kidney transplantation waiting list between 1995 and 2014, disparities in the receipt of live donor kidney transplantation increased from 1995-1999 to 2010-2014. These findings suggest that national strategies for addressing disparities in receipt of live donor kidney transplantation should be revisited.

Small Incentives Improve Weight Loss in Women From Disadvantaged Backgrounds
Tricia Leahey et al.
American Journal of Preventive Medicine, forthcoming

Methods: Data were pooled from two randomized trials in which women (N=264) received either Internet behavioral weight loss treatment (IBWL) or IBWL plus incentives (IBWL+$). Weight was objectively assessed. Data were collected and analyzed from 2011 to 2017.

Results: Women from lower-income backgrounds had significantly better weight loss outcomes in IBWL+$ compared with IBWL alone (6.4 [SD=4.9%] vs 2.6 [SD=4.6%], p=0.01). Moreover, a greater percentage achieved a ≥5% weight loss in IBWL+$ vs IBWL alone (52.6% vs 38.1%, p=0.01). Interestingly, the comparison between lower-income versus higher-income groups showed that, in IBWL alone, women with lower income achieved significantly poorer weight losses (3.4 [SD=4.2%] vs 4.9 [SD=4.0%], p=0.03). By contrast, in IBWL+$, weight loss outcomes did not differ by income status (5.0 [SD=5.6%] vs 5.3 [SD=3.8%], p=0.80), and a similar percentage of lower- versus higher-income women achieved a ≥5% weight loss (52.6% vs 53.8%, p=0.93).

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