Paul Fronstin (Employee Benefit Research Institute) has posted The Tax Treatment of Health Insurance and Employment-Based Health Benefits on SSRN.  Here is the abstract:

Various proposals have been made to change the tax treatment of health coverage, which currently is tax free to both employers and workers. Proponents of these changes argue, among other things, that current tax rules are unfair and contribute to unnecessary spending for health care. This paper examines changes that policymakers are discussing, explores the history of tax laws concerning the tax treatment of health benefits and the cost to the federal government in forgone taxes because of these laws, and examines some of the advantages and disadvantages that could result from the proposed changes. Any honest debate of overhauling the federal tax treatment of health care in the United States needs to address not just what a new system might do, but what the trade-offs and unintended consequences might be, and who would be likely to be most affected by the change.