Access to scientific data can enable independent reuse and verification; however, most data are not available and become increasingly irrecoverable over time. This study aimed to retrieve and preserve important datasets from 160 of the most highly-cited social science articles published between 2008-2013 and 2015-2018. We asked authors if they would share data in a public repository — the Data Ark — or provide reasons if data could not be shared. Of the 160 articles, data for 117 (73%, 95% CI [67% – 80%]) were not available and data for 7 (4%, 95% CI [0% – 12%]) were available with restrictions. Data for 36 (22%, 95% CI [16% – 30%]) articles were available in unrestricted form: 29 of these datasets were already available and 7 datasets were made available in the Data Ark. Most authors did not respond to our data requests and a minority shared reasons for not sharing, such as legal or ethical constraints. These findings highlight an unresolved need to preserve important scientific datasets and increase their accessibility to the scientific community.