Joshua D. Gottlieb: Research

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Abstract: We investigate whether physicians' financial incentives influence health care supply, technology diffusion, and resulting patient outcomes. In 1997, Medicare consolidated the geographic regions across which it adjusts payments for physician services, generating area-specific price shocks that are plausibly exogenous with respect to health care demand. Areas with higher payment shocks experience significant increases in health care supply. On average, a 2 percent increase in payment rates leads to a 5 percent increase in care provision per patient. Elective procedures such as cataract surgery respond twice as strongly as less discretionary services like dialysis. Higher reimbursements also increase the pace of technology diffusion, as non-radiologists acquire magnetic resonance imaging scanners more readily when prices increase. The magnitudes of our empirical findings imply that changing provider incentives explain up to one third of recent growth in spending on physician services. The incremental care has no significant impacts on mortality, hospitalizations, or heart attacks.

Paper, January 2012

Joshua Gottlieb, Alan Schwartz, Joanne Marshall, Pamela Ouyang, Linda Kern, Veena Shetty, Maria Trois, Naresh Punjabi, Cynthia Brown, Samer Najjar and Stephen Gottlieb.

Abstract:

Objectives: This study was conducted to evaluate whether brain (B-type) natriuretic peptide (BNP) changes during sleep are associated with the frequency and severity of apneic/hypopneic episodes, intermittent arousals, and hypoxia.

Background: Sleep apnea is strongly associated with heart failure (HF) and could conceivably worsen HF through increased sympathetic activity, hemodynamic stress, hypoxemia, and oxidative stress. If apneic activity does cause acute stress in HF, it should increase BNP.

Methods: Sixty-four HF patients with New York Heart Association functional class II and III HF and ejection fraction <40% underwent a baseline sleep study. Five patients with no sleep apnea and 12 with severe sleep apnea underwent repeat sleep studies, during which blood was collected every 20 min for the measurement of BNP. Patients with severe sleep apnea also underwent a third sleep study with frequent BNP measurements while they were administered oxygen. This provided 643 observations with which to relate apnea to BNP. The association of log BNP with each of 6 markers of apnea severity was evaluated with repeated measures regression models.

Results: There was no relationship between BNP and the number of apneic/hypopneic episodes or the number of arousals. However, the burden of hypoxemia (the time spent with oxygen saturation <90%) significantly predicted BNP concentrations; each 10% increase in duration of hypoxemia increased BNP by 9.6% (95% confidence interval: 1.5% to 17.7%, p = 0.02).

Conclusions: Hypoxemia appears to be an important factor that underlies the impact of sleep abnormalities on hemodynamic stress in patients with HF. Prevention of hypoxia might be especially important for these patients.

JACC, October 27, 2009 | Journal of Cardiac Failure, August 2009 (Supplement).

Data and code available here.

Abstract: Popular discussions often treat the great housing boom of the 1996-2006 period as if it were a national phenomenon with similar impacts across locales, but across metropolitan areas, price growth was dramatically higher in warmer, less educated cities with less initial density and higher initial housing values. Within metropolitan areas, price growth was faster in neighborhoods closer to the city center. The centralization of price growth during the boom was particularly dramatic in those metropolitan areas where income is higher away from the city center. We consider four different explanations for why city centers grew more quickly when wealth was more suburbanized: (1) gentrification, which brings rapid price growth, is more common in areas with centralized poverty; (2) areas with centralized poverty had more employment concentration which led to faster centralized price growth; (3) areas with centralized poverty had the weakest supply response to the boom in prices in the city center; and (4) poverty is centralized in cities with assets, like public transit, at the city center that became more valuable over the boom. We find some support for several of these hypotheses, but taken together they explain less than half of the overall connection between centralized poverty and centralized price growth.

AER P&P, May 2012 | NBER, March 2012

Abstract: Between 1996 and 2006, real housing prices rose by 53 percent according to the Federal Housing Finance Agency price index. One explanation of this boom is that it was caused by easy credit in the form of low real interest rates, high loan-to-value levels and permissive mortgage approvals. We revisit the standard user cost model of housing prices and conclude that the predicted impact of interest rates on prices is much lower once the model is generalized to include mean-reverting interest rates, mobility, prepayment, elastic housing supply, and credit-constrained home buyers. The modest predicted impact of interest rates on prices is in line with empirical estimates, and it suggests that lower real rates can explain only one-fifth of the rise in prices from 1996 to 2006. We also find no convincing evidence that changes in approval rates or loan-to-value levels can explain the bulk of the changes in house prices, but definitive judgments on those mechanisms cannot be made without better corrections for the endogeneity of borrowers' decisions to apply for mortgages.

Chapter, forthcoming | NBER, July 2010 [pdf]

Abstract: Empirical research on cities starts with a spatial equilibrium condition: workers and firms are assumed to be indifferent across space. This condition implies that research on cities is different from research on countries, and that work on places within countries needs to consider population, income and housing prices simultaneously. Housing supply elasticity will determine whether urban success shows up in more people or higher incomes. Urban economists generally accept the existence of agglomeration economies, which exist when productivity rises with density, but estimating the magnitude of those economies is difficult. Some manufacturing firms cluster to reduce the costs of moving goods, but this force no longer appears to be important in driving urban success. Instead, modern cities are far more dependent on the role that density can play in speeding the flow of ideas. Finally, urban economics has some insights to offer related topics such as growth theory, national income accounts, public economics and housing prices.

JEL, December 2009 [pdf] | NBER, March 2009.

Abstract: Should the national government undertake policies aimed at strengthening the economies of particular localities or regions? Agglomeration economies and human capital spillovers suggest that such policies could enhance welfare. However, the mere existence of agglomeration externalities does not indicate which places should be subsidized. Without a better understanding of nonlinearities in these externalities, any government spatial policy is as likely to reduce as to increase welfare. Transportation spending has historically done much to make or break particular places, but current transportation spending subsidizes low-income, low-density places where agglomeration effects are likely to be weakest. Most large-scale place-oriented policies have had little discernable impact. Some targeted policies such as Empowerment Zones seem to have an effect but are expensive relative to their achievements. The greatest promise for a national place-based policy lies in impeding the tendency of highly productive areas to restrict their own growth through restrictions on land use.

BPEA, Spring 2008 | NBER, October 2008 | HIER, November 2008.

Data and code available here.