National Institutes of Health Research Project Grant Inflation 1998 to 2021

We analyzed changes in total costs for National Institutes of Health (NIH) awarded Research Project Grants issued from 1998 to 2003. The NIH uses a data-driven price index – the Biomedical Research and Development Price Index (BRDPI) – to account for inflation based increases in grant costs. The BRDPI was higher than the general rate of inflation from 1998 until 2012; since then, the rate of inflation for NIH-funded research has been similar to the general rate of inflation. Despite increases in nominal costs, recent years have seen increases in the absolute numbers of RPG and R01 awards. Real (BRDPI-adjusted) average and median RPG costs increased during the NIH-doubling (1998 to 2003), but have remained relatively stable since. Of note, though, the degree of variation of RPG costs has changed over time, with more marked extremes observed on both higher and lower levels of cost. On both ends of the cost spectrum, the agency is funding a greater proportion of solicited projects, with nearly half of RPG money going towards solicited projects. After adjusting for potential confounders in a wholly non-parametric machine learning regression, we find no independent association of time with BRDPI-adjusted costs. ### Competing Interest Statement The authors have declared no competing interest.