Wall Street Journal op-ed, Get Ready for a 70% Marginal Tax Rate, by Michael J. Boskin (Stanford University, Hoover Institution):

President Obama has been using the debt-ceiling debate and bipartisan calls for deficit reduction to demand higher taxes. With unemployment stuck at 9.2% and a vigorous economic “recovery” appearing more and more elusive, his timing couldn’t be worse.

Two problems arise when marginal tax rates are raised. First, as college students learn in Econ 101, higher marginal rates cause real economic harm. The combined marginal rate from all taxes is a vital metric, since it heavily influences incentives in the economy—workers and employers, savers and investors base decisions on after-tax returns. … Second, as tax rates rise, the tax base shrinks and ultimately, as Art Laffer has long argued, tax rates can become so prohibitive that raising them further reduces revenue—not to mention damaging the economy. That is where U.S. tax rates are headed if we do not control spending soon.

The current top federal rate of 35% is scheduled to rise to 39.6% in 2013 (plus one-to-two points from the phase-out of itemized deductions for singles making above $200,000 and couples earning above $250,000). The payroll tax is 12.4% for Social Security (capped at $106,000), and 2.9% for Medicare (no income cap). While the payroll tax is theoretically split between employers and employees, the employers’ share is ultimately shifted to workers in the form of lower wages.

But there are also state income taxes that need to be kept in mind. They contribute to the burden. The top state personal rate in California, for example, is now about 10.5%. Thus the marginal tax rate paid on wages combining all these taxes is 44.1%. (This is a net figure because state income taxes paid are deducted from federal income.) So, for a family in high-cost California taxed at the top federal rate, the expiration of the Bush tax cuts in 2013, the 0.9% increase in payroll taxes to fund ObamaCare, and the president’s proposal to eventually uncap Social Security payroll taxes would lift its combined marginal tax rate to a stunning 58.4%.

But wait, things get worse. As Milton Friedman taught decades ago, the true burden on taxpayers today is government spending; government borrowing requires future interest payments out of future taxes. To cover the Congressional Budget Office projection of Mr. Obama’s $841 billion deficit in 2016 requires a 31.7% increase in all income tax rates (and that’s assuming the Social Security income cap is removed). This raises the top rate to 52.2% and brings the total combined marginal tax rate to 68.8%. Government, in short, would take over two-thirds of any incremental earnings. …

Nobody—rich, middle-income or poor—can afford to have the economy so burdened. … Some argue the U.S. economy can easily bear higher pre-Reagan tax rates. They point to the 1930s-1950s, when top marginal rates were between 79% and 94%, or the Carter-era 1970s, when the top rate was about 70%. But those rates applied to a much smaller fraction of taxpayers and kicked in at much higher income levels relative to today. There were also greater opportunities for sheltering income from the income tax….

There is only one solution to this growth-destroying, confiscatory tax-rate future: Control spending growth, especially of entitlements. Meaningful tax reform—not with higher rates as Mr. Obama proposes, but with lower rates on a broader base of economic activity and people—can be an especially effective complement to spending control. But without increased spending discipline, even the best tax reforms are doomed to be undone.