Here Corrections provides a powerful graph on the distortionary nature of taxation from Marco Bianchi, Bjorn R. Gudmundsson and Gylfi Zoega's paper "Iceland's Natural Experiment in Supply-Side Economics" (AER 2001). Before 1987, Icelanders had to pay taxes on the previous year's income. In 1987, they had to pay taxes on the current year's income. Consequently, 1986 had no substitution effect away from work, though taxes were still being paid. Compared to the surrounding years, there was an increase of 4.16% in real GDP. Employment jumped by 4.16% for women: to put this into perspective, this is 15% of the entire increase in the employment rate of women between 1960 and 1980, a sexual revolution.
Among the best graphs Corrections has seen in economics displaying a relatively clean natural experiment can be found below (click to enlarge).click to enlarge).