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Joseph Doyle, MIT Sloan

Curriculum Vitae



Published Papers

Measuring Returns to Hospital Care: Evidence from Ambulance Referral Patterns (with John Graves, Jonathan Gruber, and Samuel Kleiner) Journal of Political Economy. forthcoming.

Medicare spending exceeds 4% of GDP in the US each year, and there are concerns that moral hazard problems have led to overspending. This paper considers whether hospitals that treat patients more aggressively and receive higher payments from Medicare improve health outcomes for their patients. An innovation is a new lens to compare hospital performance for emergency patients: plausibly exogenous variation in ambulance-company assignment among patients who live near one another. Using Medicare data from 2002-2010, we show that ambulance company assignment importantly a.ects hospital choice for patients in the same ZIP code. Using data for New York State from 2000-2006 that matches exact patient addresses to hospital discharge records, we show that patients who live very near each other but on either side of ambulance service area boundaries go to di.erent types of hospitals. Both identification strategies show that higher-cost hospitals achieve better patient outcomes for a variety of emergency conditions. Using our Medicare sample, the estimates imply that a one standard deviation increase in Medicare reimbursement leads to a 4 percentage point reduction in mortality (10% compared to the mean). Taking into account one-year spending after the health shock, the implied cost per at least one year of life saved is approximately $80,000. These results are found across di.erent types of hospitals and patients, as well across both identification strategies.

Economics of Child Wellbeing (with Anna Aizer). In Ben-Arieh, Asher, Casas, Ferran, Frones, Ivar. and Korbin, Jill E. (Eds.) (in press) Handbook of Child Well-Being. Theories, Methods and Policies in Global Perspective . Dorcrecht: Springer.

Causal Effects of Foster Care: An Instrumental-Variables Approach Children and youth Services Review 3(7). 2013: 1143-1151.


This paper describes the use of instrumental-variables (IV) to estimate causal effects of foster care on long- and short-term outcomes. This estimation strategy provides a tool to evaluate what are known as "natural experiments": settings that mimic randomization usually associated with a controlled trial. The proposed natural experiment involves the effective randomization of investigators to child-protection cases. The results suggest that foster care placement increases like likelihood of delinquency and emergency healthcare episodes. Care must be taken when interpreting IV estimates. The results apply to cases that are part of the natural experiment-"marginal cases" where the investigators may disagree about the placement recommendation.

After Midnight: A Regression Discontinuity Design in Length of Postpartum Hospital Stays (with Doug Almond) American Economic Journal: Economic Policy. 3(3). August 2011: 1-34. Online Appendix: OLS vs. 2SLS

Estimates of moral hazard in health insurance markets can be confounded by adverse selection. This paper considers a plausibly exogenous change in insurance coverage after child birth - the most common reason for hospitalization in the US. Our identification strategy exploits insurance rules that reimburse a predetermined number of "days" in the hospital, counted as the number of midnights in care. A newborn delivered at 12:05 a.m. will have an extra night of reimbursable care compared to an infant born minutes earlier. In a dataset of California births from 1991-2002 - including nearly 100,000 births within 20 minutes of midnight - we find that the discontinuous change in insurance coverage at midnight leads to significantly longer lengths of stay for those born just after midnight compared to those born just prior to midnight. A 1997 law entitling newborns to a minimum stay of two nights allows us to consider two distinct treatments: prior to the 1997 law, the midnight discontinuity typically increased stay length from one to two nights; following the 1997 law, the midnight discontinuity increased stay length from two to three nights. On both margins, we find that remaining in the hospital longer due to a post-midnight birth has no effect on readmissions or mortality, and the estimates are precise. The results suggest that for uncomplicated births, extended minimum insurance levels are associated with substantial costs without an improvement in major health problems.

Returns to Local-Area Healthcare Spending: Using Health Shocks to Patients Far From Home American Economic Journal: Applied Economics. 3(3). July 2011: 221-243. Appendix


Healthcare spending varies widely across markets, and previous empirical studies find little evidence that higher spending translates into better health outcomes, possibly due to endogeneity bias. The main innovation in this paper compares outcomes of patients who are exposed to different healthcare systems not designed for them: patients who are far from home when a health emergency strikes. Visitors to Florida who become ill in high-spending areas have significantly lower mortality rates compared to visitors in lower-spending areas. The results are robust within groups of similar visitors and within groups of destinations that appear to be close demand substitutes-areas that likely attract similar visitors.

Returns to Physician Human Capital: Evidence from Patients Randomized to Physician Teams (with Todd Wagner & Steven Ewer) Journal of Health Economics 29(6). December 2010: 866-882.

        Winner of the 2011 KPMG Prize for the "Best Publication of the Year in Health Economics"

Physicians play a major role in determining the cost and quality of healthcare, yet estimates of these effects can be confounded by patient sorting. This paper considers a natural experiment where nearly 30,000 patients were randomly assigned to clinical teams from one of two academic institutions. One institution is among the top medical schools in the U.S., while the other institution is ranked lower in the distribution. Patients treated by the two programs have similar observable characteristics and have access to a single set of facilities and ancillary staff. Those treated by physicians from the higher-ranked institution have 10-25% less expensive stays than patients assigned to the lower-ranked institution. Health outcomes are not related to the physician team assignment. Cost differences are most pronounced for serious conditions, and they largely stem from diagnostic-testing rates: the lower-ranked program tends to order more tests and takes longer to order them.

Estimating Marginal Returns to Medical Care: Evidence from Care for At-Risk Newborns (with Doug Almond, Amanda Kowalski and Heidi Williams) Quarterly Journal of Economics. 125(2). May 2010: 591-634. Reply to Barreca, Guldi, Lindo, and Waddell

        Winner of the 2010 HCUP Outstanding Article of the Year Award
        Winner of the 2011 Garfield Economic Impact Award

We estimate marginal returns to medical care for at-risk newborns by comparing health outcomes and medical treatment provision on either side of common risk classifications, most notably the "very low birth weight" threshold at 1500 grams. First, using data on the census of US births in available years from 1983-2002, we find evidence that newborns with birth weights just below 1500 grams have lower one-year mortality rates than do newborns with birth weights just above this cutoff, even though mortality risk tends to decrease with birth weight. One-year mortality falls by approximately one percentage point as birth weight crosses 1500 grams from above, which is large relative to mean one-year mortality of 5.5% just above 1500 grams. Second, using hospital discharge records for births in five states in available years from 1991-2006, we find evidence that newborns with birth weights just below 1500 grams have discontinuously higher costs and frequencies of specific medical inputs. We estimate a $4,000 increase in hospital costs as birth weight approaches 1500 grams from above, relative to mean hospital costs of $40,000 just above 1500 grams. Taken together, these estimates suggest that the cost of saving a statistical life of a newborn with birth weight near 1500 grams is on the order of $550,000 in 2006 dollars.

Evaluating the Effectiveness of Child Safety Seats and Seat Belts in Protecting Children from Injury (Joint with Steven D. Levitt). Economic Inquiry. 48(3). July 2010: 521-536.


Young children are required to use child safety seats, and the age threshold at which children can legally graduate to seat belts has steadily increased. This paper tests the relative effectiveness of child safety seats, lap-and-shoulder seat belts, and lap belts in preventing injuries among motor vehicle passengers aged 2-6. We analyze three large, representative samples of crashes reported to police, as well as linked hospital data. We find no apparent difference in the two most serious injury categories for children in child safety seats versus lap-and-shoulder belts. Child safety seats provide a statistically significant 25% reduction in the least serious injury category. Lap belts are somewhat less effective than the two other types of restraints, but far superior to riding unrestrained.

Edgeworth Cycles Revisited (with Erich Muehlegger & Krislert Samphantharak) Energy Economics. 32(3). May 2010: 651-660.

Some gasoline markets exhibit remarkable price cycles, where price spikes are followed by a series of small price declines: a pattern consistent with a model of Edgeworth cycles described by Maskin and Tirole. We extend the model and empirically test its predictions with a new dataset of daily station-level prices in 115 US cities. Consistent with the theory, and often in contrast with previous empirical work, we find the least and most concentrated markets are much less likely to exhibit cycling behavior both within and across cities; areas with more independent convenience-store gas stations are also more likely to cycle.


Child Protection and Adult Crime: Using Investigator Assignment to Estimate Causal Effects of Foster Care Journal of Political Economy. 116(4). August 2008: 746-770.

Working Paper Version

Nearly 20% of young prison inmates spent part of their youth in foster care. This paper uses the foster care placement frequency of child protection investigators as an instrumental variable to identify causal effects of foster care on adult arrest, conviction, and imprisonment outcomes. A new dataset that links criminal justice data and child abuse investigation data in Illinois allows a comparison of adult crime outcomes across individuals who were investigated for abuse or neglect as children. Families are effectively randomized to child protection investigators through a rotational assignment process, and child characteristics are similar across investigators. Investigator placement frequencies are predictive of subsequent foster care placement, and the results suggest that children who are on the margin of placement are less likely to enter the criminal justice system when they remain at home. One innovation is the examination of the types of children most likely to be marginal cases, and the results suggest that the results apply particularly to girls, African Americans, and children investigated when they are young adolescents.

$2.00 Gas! Studying the Effects of a Gas Tax Moratorium. Journal of Public Economics 92(3-4). April 2008: 869-884. (Joint with Krislert Samphantharak)

There are surprisingly few estimates of the effect of sales taxes on retail prices, especially at the firm level. Further, along both sides of a state border, a change in one state's sales tax can shed light on the nature of competition, as a subset of firms effectively experiences a change in its marginal cost. This paper considers the suspension, and subsequent reinstatement, of the 5% gasoline sales tax in Illinois and Indiana following a temporary price spike in the spring of 2000. Earlier laws set the timing of the reinstatements, providing plausibly exogenous changes in the tax rates. Using a unique dataset of daily, gas station-level data, retail gas prices are found to drop by 3% following the suspension, and increase by 4% following the reinstatements. After linking the stations to driving distance data, some evidence suggests that the tax increases are associated with higher prices up to an hour's drive into neighboring states.


Child Protection and Child Outcomes: Measuring the Effects of Foster Care American Economic Review 97(5). December 2007: 1583-1610.


The child welfare system investigates over 2 million children each year for parental abuse or neglect, yet little is known about the effects of removing children from home and placing them in foster care. Long-term outcomes are rarely observed, and children placed in foster care likely differ from those not placed, making comparisons difficult. This paper uses the removal tendency of investigators as an instrumental variable to identify causal effects of foster care placement on a range of outcomes for school-age children and youth. A rotational assignment process effectively randomizes families to these investigators. The results suggest that children assigned to investigators with higher removal rates are more likely to be placed in foster care themselves, and they have higher delinquency rates, teen birth rates, and lower earnings. Large marginal treatment effect estimates suggest caution in the interpretation, but the results suggest that children on the margin of placement tend to have better outcomes when they remain at home, especially for older children. Supplementary Appendix

The Market for Foster Care:An Empirical Study of the Impact of Foster Care Subsidies (Joint with H. Elizabeth Peters). Review of Economics of the Household 5(4). December 2007: 329-351.

When parents are suspected of child abuse or neglect, their children may be placed with foster families. We estimate the relationship between the monthly subsidies paid to these families and the quantity of foster care services provided. The empirical model uses variation in subsidies and foster care populations within thirty-seven states and the years 1987-1995. One innovation in our approach is that we exploit the idea that states do not appear to set market clearing rates, as evidenced by a foster home shortage during this time period. In this case of excess demand, variation in the monthly subsidy traces out the supply curve. Our results show that states with high demand may be able to use economic incentives. (Note: the publication is also available at www.springer.com


Canít Buy Me Love?Subsidizing the Care of Related Children. Journal of Public Economics 91. February 2007: 281-304.


Little is known about the effect of economic incentives on the willingness to care for relatives, as prices are difficult to measure and typically endogenous. This paper uses a reform in Illinois that reduced the wage offered to relatives asked to provide foster care as a plausibly exogenous change in the cost of caring for related children. Families first contacted just prior to the reform have a substantially higher relative placement rate compared to families contacted after the reform. Children who require mental health services, infants and teenagers appear to be on the margin of relative placement. The estimates are robust to controls, including a sample selection correction that uses the random assignment of investigators to predict entry into the sample. Meanwhile, child health, educational, and placement outcomes do not appear to suffer after the reform. The lower wage may have discouraged those foster parents less interested in child well being, mitigating the effects of the lower subsidy on child outcomes.

Health Insurance, Treatment and Outcomes: Using Automobile Accidents as Health Shocks Review of Economics and Statistics, May 2005, 87(2): 256-270. NBER Working paper version


Previous studies find that the uninsured receive less health care than the insured, yet differences in health outcomes have rarely been studied. In addition, selection bias may partly explain the difference in care received. This paper focuses on an unexpected health shock-severe automobile accidents where victims have little choice but to receive treatment. Another innovation is the use of a comparison group that is similar to the uninsured: those who have private health insurance but do not have automobile insurance. The medically uninsured are found to receive twenty percent less care and have a higher mortality rate compared to patients with health insurance. It appears that the ability-to-pay of patients has a significant effect on treatment decisions and additional treatment yields large improvements in health outcomes.



Working Papers

Juvenile Incarceration, Human Capital and Future Crime: Evidence from Randomly-assigned Judges (with Anna Aizer). June 2013.

        Winner of the 2014 National Council on Crime and Delinquency Baird Award for Outstanding Applied Research

Measuring Returns to Hospital Care: Evidence from Ambulance Referral Patterns. (With John Graves, Jonathan Gruber and Samuel Kleiner). November 2012.

Returns to Specialist Care: Evidence from Supply Shocks. May 2013.

Employment Effects of a Minimum Wage: A Density Discontinuity Design Revisited. November 2007.



Child Welfare Presentation

Child Welfare Presentation