Importance: Despite progress in narrowing gender-based salary gaps, notable disparities persist in the scientific community. The significance of pay difference may be underestimated, with little data evaluating its effect on lifetime wealth after accounting for factors like time to promotion and savings. Objectives: To characterize gender disparities in salary and assess the outcomes associated with a gender equity initiative (GEI). Design, Setting, and Participants: Quality improvement study with simulations of salary and additional accumulated wealth (AAW) using retrospectively reviewed Johns Hopkins University School of Medicine annual salary and promotion data. All academic faculty were included in the faculty salary analysis from 2005 (n = 1481) and 2016 (n = 1885). Main Outcomes and Measures: Salary and longitudinal promotion data from 2005 to 2016 were used to estimate gender-based differences in salary and time to promotion. The effect of these differences on total salary and AAW, including retirement and salary-based investments, was simulated for a representative male and female faculty member over a 30-year career in 3 scenarios: (1) pre-GEI, (2) post-GEI, and (3) in real time for GEI, beginning with and progressing through these initiatives. Results: Analyses of salaries of 1481 faculty (432 women) in 2005 and 1885 faculty (742 women) in 2016 revealed that a decade after GEI implementation, the overall mean (SE) salary gap by gender decreased from -2.6% (1.2%) (95% CI, -5.6% to -0.3%) to -1.9% (1.1%) (95% CI, -4.1% to 0.3%). Simulation of pre-GEI disparities correlated with male faculty collecting an average lifetime AAW of $501 416 more than the equivalent woman, with disparities persisting past retirement. The AAW gap decreased to $210 829 in the real-time GEI simulation and to $66 104 using post-GEI conditions, reflecting success of GEI efforts. Conclusions and Relevance: Even small gender-based salary gaps are associated with substantial differences in lifetime wealth, but an institutional commitment to achieving equitable promotion and compensation for women can appreciably reduce these disparities. The findings of this study support broad implementation of similar initiatives without delay, as results may take more than a decade to emerge. A modifiable version of the simulation is provided so that external users may assess the potential disparities present within their own institutions.