Are progressive income taxes a stable source of revenue?

RealClearMarkets - State Taxes Produce Wild Revenue Swings

More surprising, but ultimately logical, are the results from states with flat income taxes. The usual expectation is that flat taxes will produce more stable revenues than progressive income taxes that rely disproportionately on high earners. This is because high income people tend to have volatile incomes that move sharply with overall economic performance.

However, five of the seven states with flat taxes saw income tax revenue drops above the 11.4% national average. While Pennsylvania and Utah outperformed most states with drops under 9%, Indiana's flat tax saw a 20.3% drop in collections, and the four others ranged from 11.7% to 14.3%. Meanwhile, New York and New Jersey (which have graduated income taxes that rely heavily on high-income taxpayers) saw revenue drops under 9%.

Progressives will point to these results as evidence that graduated taxes do not promote revenue instability. They are wrong. What has happened is that states with flat income taxes have resisted political impulses to raise income taxes. Meanwhile, states with sharply graduated taxes have tended to impose (often sharp) income tax hikes for the current fiscal year. If states like New York and New Jersey hadn't raised taxes, their revenue performance would be among the worst in the country.

No state with a flat tax raised its income tax this year. However, eight states with graduated income taxes raised rates: Connecticut, California, Delaware, Hawaii, New Jersey, New York, Oregon and Wisconsin. Most of these personal income tax increases were in the form of new or increased "Millionaire's Taxes", which contrary to the name may be imposed on incomes as low as $125,000. The sole exception is California, which raised tax rates across the board including in its millionaire bracket.