Fine wine, art, and medical physicist bibliometrics: Things that improve with age.
TL;DR
Scholarly productivity in radiation therapy medical physics faculty at leading cancer centers is strongly dependent on career age, with peak output occurring near the end of a typical career before declining modestly near retirement.
Abstract
Purpose
Bibliometric indicators are widely used to evaluate faculty productivity, yet these metrics change with career stage, evolving authorship practices, and technological shifts in how science is produced. This study examines patterns of scholarly output among radiation therapy medical physics faculty at leading cancer centers and provides a framework and quantitative metrics for managing career age- and era-based effects.
Methods
Peer-reviewed articles (1969-2025) were collected from Scopus for 397 Ph.D. medical physics faculty at the 20 U.S. cancer centers most highly ranked by US News and World Report in 2025. The bibliometric measures included annual rates of authorships ( A ̇ ), first/last authorships ( F L ̇ ), monograph-equivalents ( M E ̇ ), as well as the cumulative h-index and contribution-normalized ha-index. Career age was defined by year of first publication. Productivity distributions were evaluated by career age using empirical cumulative distribution functions derived from 2016-2025 data. Era-dependent fluctuations (1990-2025) were examined using age-normalized metrics and trends in authorship team size. Tabulated bibliometrics as a function of career age are provided for evaluation of individual performance.
Results
Productivity increased substantially with career age, peaking in late career. Senior faculty produced approximately two-fold higher annual output than early-career peers. At career ages of 1, 10, 20, 30, and 40 years, the median bibliometric rates were A ̇ = (1.2, 1.6, 2.5, 2.5,1.8) year-1, F L ̇ = (0.4, 0.4, 0.5, 0.5,0.2) year-1, M E ̇ = (0.2, 0.2, 0.3, 0.3,0.3) year-1, h-index = (0, 7, 15, 23,43), and ha-index = (0, 3.3, 6.0, 9.4,15.0). Era-based effects were substantial. Between 1990 and 2025, median authors per paper increased from 4 to 10, inflating authorship-based metrics. In contrast, contribution-weighted measures (FL, ME, ha-index) demonstrated greater temporal stability.
Conclusions
Scholarly productivity in radiation therapy medical physics is strongly dependent on career age, with peak output occurring near the end of a typical career before declining modestly near retirement. Career-age-based percentile benchmarks provide a more balanced framework for evaluating academic performance than unadjusted bibliometric comparisons, especially for early-career investigators. Due to changes in authorship norms over time, first/last authorships, monograph equivalents, and ha-index may provide more accurate and equitable assessments of research performance than authorships or h-index.