Capital gains tax rates in the U.S. have fluctuated since they were introduced nearly a century ago, with maximum rates on long-term gains (assets held longer than one year) ranging from 77% in 1918 to as low as 15% from the last decade up through 2012. As a result of the American Taxpayer Relief Act of 2012, the top marginal tax rate on long-term capital gains income was bumped up to 20%, plus a 3.8% tax on unearned income was added to fund the Affordable Care Act and is imposed on those with an adjusted gross income of $200,000 or more (or married couples with $250,000 or more and filing jointly).

Capital gains income is also taxed at the state level, and some states come down harder than others. After taking into account the state deductibility of federal taxes and the phase-out of itemized deductions for high-income people, the top marginal tax rates on capital gains (combined federal and state) range from 25% in the nine states that don’t have a personal income tax to 33% in California, according to the Tax Foundation, an independent tax policy research organization in Washington, D.C.

The average rate in the U.S. is 28.7%, which is the sixth-highest rate in the industrialized world as represented by the 34 member nations of the Organization for Economic Co-operation and Development (OECD).

The Tax Foundation says the six states with the highest marginal tax rates on capital gains (California, New York, Oregon, Minnesota, New Jersey and Vermont), along with the District of Columbia, would make the top 10 list in a combined roster of all 50 states and the 34 OECD nations.

The Tax Foundation believes current capital gains rates in the U.S. put a heavy tax burden on saving and investment, as well as hinder economic growth. In a recent report, the organization posited that lowering taxes on capital income would reverse those effects by increasing investment and producing greater economic growth.

While such a conclusion will elicit amens from the anti-tax crowd, not everybody agrees with that premise. Warren Buffett, for one, wrote in a New York Times op-ed piece in 2012 that he didn’t see anyone forgo the investment opportunities he offered when he was managing funds during the 1950s and 1960s, when the maximum long-term capital gains rate was 25%.

And various studies from academia and the government haven’t found a concrete correlation between tax rates and economic growth. Two years ago, an economic analysis of the top tax rates since 1945 (both the top marginal tax rate and the top capital gains tax rate) by the Congressional Research Service, a legislative branch agency within the Library of Congress that works exclusively for the U.S. Congress, found no conclusive evidence to substantiate a clear relationship between the 65-year steady reduction in the top tax rates and economic growth. “Analysis of such data suggests the reduction in the top tax rates have had little association with saving, investment or productivity growth,” according to the study. “However, the top tax rate reductions appear to be associated with the increasing concentration of income at the top of the income distribution.”

Nobody likes to pay taxes. But in the emotionally charged debate over taxes, black-and-white conclusions often ignore the multiple shades of gray embedded in this complicated issue.