Application in Parallel to U.S. Residency Training Programs in Multiple Specialties: Trends and Differences by Applicant Educational Background, 2009-2021.

Purpose: The medical education community is pursuing reforms addressing unsustainable growth in the number of residency applications per applicant and application costs. Little research has examined the prevalence or contributions of parallel applications (application to residency in multiple specialties) to this growth.

Method: A retrospective analysis of Electronic Residency Application Service® data provided by the Association of American Medical Colleges was conducted. The percentage of applicants applying to ≥1 specialty, mean number of specialties applied, number of submitted applications, and percentage of applicants to each specialty who were parallel applying were determined. MD, DO, and international (U.S. international medical graduate [IMG] and IMG) applicants were included.

Results: The sample contained 586,246 applicant records from 459,704 unique applicants. The percentage of applicants who parallel applied decreased from 41.3% to 35.4% between 2009 and 2021. DO applicants were the only group for whom the percentage parallel applying increased (30.6% vs. 32.1%). IMG (60.4% vs. 49.1%) or USIMG applicants (69.6% vs. 63.1%) were groups with the greatest percentage of applicants parallel applying each year (2009-2021). The mean number of specialties applied to when parallel applying also decreased from 2.96 in 2009 to 2.79 in 2021, overall. Between 2009 and 2021, mean number of applications increased for all applicant types amongst both single-specialty applicant and parallel-applying applicants. Among applicants who were single-specialty applying, mean number of applications grew from 38.6 in 2009 to 74.6 in 2021 and from 95.2 to 149.8 for parallel-applying applicants.

Conclusions: All applicant groups experienced decreases in percentages parallel applying except for DO applicants. Parallel application appears to be common and slowly declining, and does not appear to significantly contribute to increasing numbers of applications per candidate. Efforts to control the growth of applications per applicant should continue to focus on applicants' numbers of applications submitted to each specialty.