The Congressional Budget Office has issued Taxing Capital Income: Effective Rates and Approaches to Reform (44 pages).  From the Preface:

This Congressional Budget Office (CBO) paper, prepared at the request of the Chairman of the House Ways and Means Committee, examines the taxation of capital income under current law and explores some potential alternatives to that system. In its analysis, CBO used the framework of effective tax rates to determine how heavily and uniformly capital income is taxed. It also used that framework to assess scenarios that would ultimately move the present system toward one that does not tax capital income. In keeping with CBO’s mandate to provide objective, impartial analysis, the paper makes no recommendations.