The Value of (Sub) Specialization: Evidence from Oncology

We estimate the returns to specialization in medical oncology, in which subspecialists focus on specific cancer types. Using 2.2 million Medicare chemotherapy episodes from 2008–2020, we instrument for subspecialist access with differential distance to cancer-type-specific subspecialists versus general oncologists. Access to a relevant subspecialist reduces three-year mortality by 4.5 percentage points (10 percent), without increasing Medicare spending or measured provider fragmentation. Subspecialists also increase the use of newer therapies and diagnosis-specific clinical trials. These findings show that specialization raises productivity when expertise is closely matched to the task.