The Tax Foundation has released Double-Taxing Capital Income: How Bad Is the Problem? (Fiscal Fact No. 71), by Patrick Fleenor:

[T]he statutory federal rate on corporate income is 35 percent. In the simplest type of comparison, then, this corporate rate is added to the statutory rate on individuals’ capital income, currently 15 percent, for a total tax rate of approximately 50 percent in the U.S., while it is significantly lower in many other nations.