This is the Congressional Budget Office (CBO) Cost Estimate as ordered reported by the House of Representatives on December 4, 2020. From the Document: "H.R. 3884 would federally decriminalize cannabis (marijuana), expunge the records of people convicted of federal cannabis offenses, and require resentencing of some federal prisoners. As a result, CBO estimates, thousands of current inmates would be released earlier than under current law. In the future, decriminalization also would reduce the number of people in federal prisons and the amount of time federal inmates serve. In total, over the 2021-2030 period, CBO estimates that H.R. 3884 would reduce time served by 73,000 person-years, among existing and future inmates. CBO's analysis accounts for time served by offenders convicted of cannabis-only crimes and by those convicted of another crime in addition to a cannabis offense. Federal prisoners generally are not eligible for federal benefit programs. By reducing the prison population, CBO estimates, H.R. 3884 would increase the number of federal beneficiaries, compared with current law, and thus increase direct spending for federal benefit programs by $636 million over the 2021-2030 period. CBO and the staff of the Joint Committee on Taxation estimate that H.R. 3884 would increase revenues, on net, by about $13.7 billion over the 2021-2030 period by creating business income, compliance, and occupational taxes; those increases would be partially offset by allowing certain deductions for business expenses associated with trafficking controlled substances."
Congressional Budget Office: https://www.cbo.gov/