A data point on the conservative side

The Wall Street Journal's David Wessel has a useful primer on basic U.S. tax facts today. While highlighting the top one percent's increased share of nation wealth, Wessel also notes:

From Ronald Reagan to Barack Obama, the tax code has been tweaked and the economy has had its ups and downs, and the share of federal taxes paid by the top 5% and the top 1% has risen faster than their share of income:

In the 1980s, the top 5% averaged 22.6% of income and paid 28.5% of taxes.
In the 1990s, the top 5% averaged 25.3% of income and paid 34.3% of taxes
In the 2000s, the top 5% averaged 28.4% of the income and paid 40.3% of the taxes.

If taxes for the wealthy have been radically cut (which they have), and the share of national wealth captured by the top 1% has radically grown (which it has), how can the share of federal taxes paid by the wealthy have shrunk?

I'm in Mitt Romney's tax bracket...

not really, but in 2011 my wife and I paid the same 14% (roughly) in federal taxes on our income as he did. Which seems not right, since his household income is over 100 times ours.  In any case, the Romneys and the Galeota-Sprungs are among the two thirds of American households that, according to David Leonhardt, pay less than 15% of their income in federal taxes.

Our tax return is an interesting cross-section of the current federal tax system -- in one way quite typical (net result) and in another not so typical (how we got there). While my wife is a salaried worker, I am self employed, and that introduces somewhat self-canceling distortions. The two salient features are the self-employment tax, which doubles Social Security and Medicare taxes on income up to $106,800, and  the individual 401k, created in I think 2005 for solo self-employed taxpayers, which allows solo self-employed people over 50 to contribute up to $54,000 yearly to their retirement plans, deducting that contribution from their taxable income.