Optimal marginal income tax rates

In the United States the marginal tax rates (ie, what the wealthy pay for what they earn above a certain threshold ) of the income tax were very high after the second world war. In the recent decades, they declined dramatically.
The debate on this issue has been reactivated as a result of French president Hollande 's promise to raise the marginal rate of the income tax to 75 % (the promise has been  fulfilled, but for a very high threshold and for corporations, which has received protests from the rich, especially football clubs), and the movement "Occupy Wall Street", which had as one of its slogans "We are the 99 %" , as a reference to the fact that economic growth in recent decades only benefited the richest 1%.
Apart from the historical evidence, the interesting thing is that the best economists who have studied this believe that a top marginal rate above 70 % is desirable,  meaning that it is socially optimal, because contrary to what the right says, it would not create a major disincentive to wealth creation, and would allow for ambitious distributional programs.
Paul Krugman has repeatedly referred to this in his blog, for example here and here.
There is a very interesting book with articles by some of the leading experts on the subject (Sáez, Piketty, Diamond) which is the "Occuppy Handbook". It is a very interesting book with articles by leading economists of the highest academic level that support progressive proposals. Incidentally, it is interesting that this book does not show any Spanish economist.