Earning a bachelor's degree is increasingly important to an individual's longer-term economic prospects. Communities, at all levels, also benefit when their members earn postsecondary credentials, through improved economic, social, and health outcomes. Yet, despite an increase in college participation over the last two decades, severe inequities in bachelor's degree attainment remain; inequities that often leave lower-income and BIPOC (Black, Indigenous and people of color) students with debt and no or low-value credentials. In this issue brief, the authors describe a package of four federal policy changes that would operate together to both prompt and facilitate selective colleges and universities to expand opportunity for lower-income students. The first two policies would set clear federal expectations around socioeconomic diversity and incentivize selective institutions to adhere to them: requiring a minimum share of lower-income undergraduate enrollment to participate in federal student aid and granting relief from a tax on high endowments in exchange for increasing the share of lower-income undergraduates. The two other policies will make it easier for institutions to follow through and increase the transparency of their efforts. One would expand an existing antitrust exemption to enable more institutions to reduce competitive practices that undermine socioeconomic diversity if they achieve demonstrable progress on increasing socioeconomic diversity. Finally, the authors discuss measures to improve the data on student socioeconomic status that will permit policymakers, the public, and colleges themselves to better implement and monitor the full set of policies.