The Pew Charitable Trusts have posted an analysis comparing the volatility of the tax systems of the fifty states. The index Pew uses for volatility is the standard deviation of year-over-year percent change of each state’s total tax revenue from 1994 to 2013, adjusted for all known tax changes.

Alaska has the highest volatility score, 34.4 percent; South Dakota has the lowest score, 2.6 percent. Washington volatility score, 4.2 percent, was lower than those of 37 other states.

(Click on the chart to go to the Pew website.)

The key points from Pew’s analysis:

• Overall, 50-state tax revenue had a volatility score of 5.0 percent. Compared with this national benchmark, 29 states had higher volatility and 21 had lower.
• Three of the four states with the greatest overall volatility received a substantial share of their tax dollars from severance taxes, which are affected by global energy prices. In 2013, severance taxes made up 78.3 percent of tax revenue in Alaska, 39.7 percent in Wyoming, and 46.4 percent in North Dakota.
• Among the states with low overall scores, Kentucky collected the bulk of its tax dollars from some of the least volatile personal income and sales tax streams in the country, and South Dakota relied primarily on one of the most stable streams of sales tax revenue.
• Corporate income tax revenue seesawed more than any other tax source in 24 of the 29 states where it was a major tax, and it was more volatile than personal income tax in all 25 states that collected both as a major tax. Its volatility score ranged from 59.0 percent in Alaska to 9.3 percent in New Hampshire.
• Severance tax was the most volatile revenue source in six of the nine states where it was a major tax, with volatility scores ranging from 39.7 percent in Alaska to 15.3 percent in West Virginia.
• Personal income tax fluctuated more than any other type of tax in nine of the 41 states that levy it. Volatility scores ranged from 13.4 percent in North Dakota to 3.5 percent in West Virginia.
• Sales tax was the most volatile major tax in only three of the 45 states that impose it: Nevada and Washington, which have no personal income tax, and Colorado, the only state where sales tax was more volatile than personal income tax among 38 states that collect both. Volatility scores for sales tax ranged from a high of 14.9 percent in Wyoming to a low of 2.8 percent in Kentucky.

The volatility score for Washington’s sales tax is 5.2 percent, which ranks 21st among the 45 states with a sales tax.