Abstract
Open science reforms have made posting data and code common, but are shared materials actually used, and easily reused? Treating download counts of Open Science Framework (OSF) supplements as a usage index, I analysed 1,660 articles from four psychology journals (Cognition, Psychological Science, Journal of Experimental Social Psychology, Journal of Memory and Language) across three years (2015, 2020, 2025). OSF sharing rose from 9% in 2015 to 82% in 2025. Among 652 papers with download data, materials were downloaded a median of 135 times; fewer than 1% went undownloaded. Download volume was associated with citation count and altmetric attention. Availability did not ensure easy reuse: only 30% of repositories provided documentation, 34% were flagged for a hard-coded file path, and 40% referenced a missing file —shortcomings that did not improve as sharing grew. Altogether, shared materials are being used, but often not easily reusable