Tax cuts do exactly what you would think, they make rich people richer and don't stimulate the economy.
“countries that made large cuts in top tax rates such as the United Kingdom or the United States have not grown significantly faster than countries that did not, such as Germany or Denmark.”
What does show a strong correlation is falling tax rates and the share of pre-tax income held by the top 1 percent — which has more than doubled in the U.S., to more than 20 percent, over the past 40 years. Piketty, Saez and Stantcheva offer three possible explanations for what happens after a tax cut: 1) the wealthy work harder; 2) they hide less of their income from the government; 3) they bargain harder for higher pay. Long story short, the authors endorse No.3. As they say, “executives can be overpaid if they are entrenched and can use their power to influence compensation committees.”