||Cumulative advantage – commonly known as the Matthew Effect – influences scientific output and careers. Given the challenge and uncertainty of gauging the quality of new scientific research, evaluators and gatekeepers often possess incentives to prefer the work of established scientists. Such preferences breach scientific norms of fairness, and can yield suboptimal research outcomes. This article analyzes repeat authors as an exemplar of the Matthew Effect. Although a scientist publishing in the same journal multiple times is rare within individual careers, the phenomenon is relatively common at the level of scientific journals. Using publication data for 347 economics journals from 1980-2016, we analyze whether articles written by repeat authors tend to fare better or worse than less-experienced authors. Random effects models show a curvilinear (inverted U-shaped) relationship between repeat authorship and citation impact. In these models, citation impact peaks at the fourth repeat publication, suggesting both liabilities of newness and liabilities of senescence in science. Fixed effects models show that within individual scientific careers, authors tend to be most impactful with their debut publication, then experience declining impact with each subsequent repeat authorship. Implications for innovation incentives for scientists and gatekeepers alike are discussed.