Making scientific literature freely available to everyone is a main objective of the open access (OA) movement. This may be especially crucial for researchers in lower-income countries who often face barriers due to high subscription costs. In this paper, we address this issue by analyzing the reference lists of scientific publications worldwide over time. Our study focuses on key issues, including whether researchers from lower-income countries refer to fewer previous publications when they publish and how this trend evolves over time. We also investigate whether researchers from lower-income countries rely more on literature that is openly available through different OA routes compared to other researchers. Our study reveals that the proportion of references that are OA is increasing over time for all publications and country groups. However, publications from lower-income countries have a higher growth rate of OA-references, suggesting that the emergence of OA-publishing has been particularly advantageous for researchers in these countries.