Why James Stewart's Production Is Down

James B. Stewart, the prize winning author, and NYTimes columnist sat down with a calculator to compute his tax rates and reports here.  The results:

I paid 24 percent of my adjusted gross income in federal taxes and 37 percent in combined federal, state and local income taxes. I paid 49 percent of my taxable income in federal income tax, and 74 percent of my taxable income in combined federal, state and local income taxes. My totals include federal payroll and self-employment taxes.

 No wonder his productivity over recent years has been down--he pays too much in taxes--that's the logic conservative economists would use.  His picture reflects his self-employment and living in NYC.  I'm too lazy to check but I think the usual figure for comparison is the AGI percentage (i.e., Gingrich paying 30+, Obamas 25+, Romney 14+).

This led me to a thought though: Mr. Stewart may well have slowed down some recently, but is that more the effect of incentives/taxes or is it the effect of aging. Much discussion of the impact of taxes on incentives omits any correction for age.

[updated: corrected typo]