Publications
2026
Primary Care Clinicians Available for New Patient Visitswith Katherine Majzoub Morgan and Michael L. Barnett, JAMA Internal Medicine
Published Version
Abstract
Amid concern that finding a new primary care physician (PCP) in the US is increasingly difficult, US adults without a usual source of care increased from 21% in 2013 to 30% in 2022. While the declining number of practicing PCPs is well described, a recent trend in PCPs reducing panel sizes calls for new methods to measure the supply of primary care services. While there is hope that primary care advanced practice clinicians (APCs) might mitigate the PCP shortage, whether this is happening is unclear. We examined trends in new patient primary care visits as a measure of the supply of PCPs and primary care APCs.
2025
Intergenerational Mobility Trends and the Changing Role of Female Laborwith Ulrika Ahrsjö and Joachim Kahr Rasmussen, Journal of Human Resources
Published Version · arXiv
Abstract
Using harmonized administrative data from Scandinavia, we find that intergenerational rank associations in income have increased uniformly across Sweden, Denmark, and Norway for cohorts born between 1951 and 1979. By gender, father-son mobility remains stable, while correlations for mothers and daughters rise. Similar patterns appear in US survey data, albeit with different timing. We show that the decline in income mobility reflects a stronger link between female income and underlying productivity, rather than stronger intergenerational transmission of human capital or changes in assortative mating. Finally, we show that parent-child correlations increase mainly when women gain access to jobs that match their productivity.
with David C. Chan, Bruce E. Landon, Nancy L. Keating, Christopher Manz, Jukka-Pekka Onnela, Thomas C. Tsai, Yuhua Zhang, and Michael L. Barnett, JAMA Health Forum
Published Version
Abstract
Importance: Subspecialists—physicians with narrower clinical focus—play an increasing role in US health care, particularly in surgery, where most trainees now pursue fellowship training. Yet little is known about the degree of subspecialization among practicing surgeons and the evolving role of surgical generalists.
Objective: To quantify trends in surgical subspecialization and examine the geographic distribution of subspecialists and the procedural scope of surgical generalists.
Design, Setting, and Participants: A retrospective cohort study using 100% Medicare Part B data from 2000, 2010, and 2021, including all fee-for-service beneficiaries treated by physicians in general surgery, neurosurgery, ophthalmology, orthopedic surgery, and otolaryngology was caried out. A novel classification method combining k-means clustering, large language models, and expert validation to distinguish subspecialists from surgical generalists based on procedural claims was used. The analysis was undertaken in 2023 and 2024.
Main Outcomes and Measures: The number of distinct subspecialties, the share of subspecialists in each surgical specialty, their geographic distribution across hospital referral regions (HRRs), and the association between subspecialist supply and procedural diversity among generalists.
Results: Overall, more than 70 000 surgeons were included. The share of subspecialists increased from 38% in 2000 to 58% in 2021, reflecting the growth of recognized subspecialties (from 24 to 33) and expansion of existing ones. Subspecialization rates varied by specialty, rising from 9% to 28% in otolaryngology and from 66% to 77% in neurosurgery. While subspecialist supply per 100 000 fee-for-service beneficiaries remained stable, the mean number of surgical generalists per 100 000 declined from 105 to 50. A 10% increase in subspecialist supply in an HRR was associated with a 0.94% decrease (95% CI, –0.15% to –0.41%) in the number of unique procedures performed by generalist surgeons.
Conclusions and Relevance: This cohort study found that subspecialization has considerably reshaped the surgical workforce, concentrating care among subspecialists while narrowing the procedural scope of generalist surgeons. These shifts raise concerns about access to generalist care, particularly in regions with declining generalist supply, and suggest the need for policies that consider both specialization and geographic equity in surgical workforce planning.
with Christopher Manz, Arno Cai, David C. Chan, Bruce E. Landon, Nancy L. Keating, Jukka-Pekka Onnela, and Michael L. Barnett, Annals of Internal Medicine
Published Version
Abstract
Background: The growing complexity of cancer care may be driving an increase in subspecialized medical oncologists who focus on treating specific cancer types. However, little is known about trends in subspecialization among oncologists and differences in utilization of subspecialists.
Objective: To quantify trends in oncologist subspecialization and assess differences in utilization of subspecialized cancer care in the United States.
Design: Retrospective cohort study using Medicare claims data from 2007 to 2021.
Setting: National, fee-for-service Medicare.
Participants: Medicare beneficiaries initiating chemotherapy between 2008 and 2020.
Measurements: Chemotherapy episodes were defined using methods from the Oncology Care Model. Subspecialization was identified based on whether oncologists managed more than 80% of chemotherapy episodes within a single cancer category. Outcomes included the annual share of oncologists classified as subspecialists, and the share of chemotherapy episodes managed by these oncologists, stratified by cancer type, geography, and socioeconomic characteristics.
Results: Among 18 633 oncologists and 9.25 million chemotherapy episodes, the proportion of episodes managed by subspecialists increased from 9% in 2008 to 18% in 2020. Utilization varied widely across cancer types and regions, with the highest levels observed in large metropolitan areas. Differences by income widened over time: in 2020, 27.6% of episodes in the highest-income counties were managed by subspecialists, compared with only 8.8% in the lowest-income counties, despite higher cancer mortality in the latter.
Limitations: Analyses were limited to fee-for-service Medicare beneficiaries and excluded patients treated with surgery or radiation alone. Subspecialization was defined using practice patterns rather than formal training, and the study does not assess patient outcomes or causal effects.
Conclusion: Subspecialization in oncology is increasing but is unevenly distributed, with growing differences in utilization across income groups and regions.
Primary Funding Source: National Institute on Aging.
with Aline Bütikofer and Alexander Willén, Journal of Public Economics
Published Version · Working Paper
Abstract
Childbirth raises the opportunity cost of commuting and makes it difficult for both parents to work far away from home. Using detailed Norwegian employer-employee matched register data, we show that the commuting behavior of men and women diverges immediately after childbirth and that those differences persist for at least a decade. This divergence in commuting behavior exposes mothers to more concentrated and rural labor markets with fewer job opportunities and lower establishment quality. These findings uncover a key mechanism underlying the child penalty documented in prior work and have important implications for the design of policies seeking to address the remaining gender wage gap.
2021
Inequality in Mortality between Black and White Americans by Age, Place, and Cause, and in Comparison to Europe, 1990–2018with Hannes Schwandt, Janet Currie et al., Proceedings of the National Academy of Sciences
Published Version · NBER Working Paper
Abstract
Although there is a large gap between Black and White American life expectancies, the gap fell 48.9% between 1990 and 2018, mainly due to mortality declines among Black Americans. We examine age-specific mortality trends and racial gaps in life expectancy in high- and low-income US areas and with reference to six European countries. Inequalities in life expectancy are starker in the United States than in Europe. In 1990, White Americans and Europeans in high-income areas had similar overall life expectancy, while life expectancy for White Americans in low-income areas was lower. However, since then, even high-income White Americans have lost ground relative to Europeans. Meanwhile, the gap in life expectancy between Black Americans and Europeans decreased by 8.3%. Black American life expectancy increased more than White American life expectancy in all US areas, but improvements in lower-income areas had the greatest impact on the racial life expectancy gap. The causes that contributed the most to Black Americans’ mortality reductions included cancer, homicide, HIV, and causes originating in the fetal or infant period. Life expectancy for both Black and White Americans plateaued or slightly declined after 2012, but this stalling was most evident among Black Americans even prior to the COVID-19 pandemic. If improvements had continued at the 1990 to 2012 rate, the racial gap in life expectancy would have closed by 2036. European life expectancy also stalled after 2014. Still, the comparison with Europe suggests that mortality rates of both Black and White Americans could fall much further across all ages and in both high-income and low-income areas.
with Aline Bütikofer and Kjell G. Salvanes, Fiscal Studies
Published Version · Working Paper
Abstract
While Norway has experienced income growth accompanied by a large decline in mortality during the past several decades, little is known about the distribution of these improvements in longevity across the income distribution. Using municipality level income and mortality data, we show that the stark income gradient in infant mortality across municipalities in the 1950s mostly closed in the late 1960s. However, the income gradient in mortality for older age categories across municipalities persisted until 2010 and only flattened thereafter. Further, the infant mortality gap between rich and poor Norwegian families based on individual-level data persisted several decades longer than the gap between rich and poor municipalities and only finally closed in the early 21st century.