Not much, according to Allen Meltzer:
[T]he share of income for the top 1% in [U.S., Sweden, France, Australia, Britain, Canada and the Netherlands] generally follows the same trend line [from the early 1900s to 2004]. That means domestic policy can't be the principal reason for the current spread between high earners and others. Since the 1980s, that spread has increased in nearly all seven countries. The U.S. and Sweden, countries with very different systems of redistribution, along with the U.K. and Canada show the largest increase in the share of income for the top 1%.
Daron Acemoglu and James Robinson, armed with data in the above chart, counter:
[T]he US — to some degree together with the UK — stands apart from others in terms of the extent of the increase in the share of the top one percent in national income. The [above chart] summarizes this pattern and shows that the top one percent’s share increased little or not at all in several European countries.
The Dish 