Recent academic research findings on topics relating to taxation and social insurance policy, including the implicit tax imposed by Medicaid on private long-term care insurance benefits, an alternative system of unemployment insurance, and federal energy tax policy.This NBER series presents current academic research findings in the areas of taxation and government spending. The papers included provide important background information for policy analysts in government and the private sector without making specific policy recommendations. This twenty-first installment in the series reports on recent research concerning both taxation and social insurance policy. The papers discuss Medicaid's implicit tax on the benefits of private long-term care insurance, an alternative to current unemployment insurance systems, the tax treatment of health insurance expenditures, the effective marginal tax rates on labor supply and saving, and the rationale for and effect of energy-related tax policies.