56% is a low top marginal tax rate. The United States had a top marginal income tax rate that was higher than 56% between 1932 and 1980. It was 90% between 1950 and 1963.
http://www.taxpolicycenter.org/taxfacts/displayafact.cfm?Doc...
Reducing the marginal tax rates on income in the US was largely revenue neutral due to the incremental elimination of loopholes, credits, and deductions concurrent with those reductions. If we actually reverted to the tax policies of 1950s I do not think you would be impressed with the distribution of taxes paid.
Ironically, the low marginal tax rates we have today reflect the historical truth more closely than the nominally high rates of the past.
That said, to reach the top income bracket and get a tax between 52-59.9% (Depending on where in Sweden you live) you have to earn somewhere around $80k/yr. Not entire sure about the number but it is in that region. I wouldn't consider that very wealthy, especially not if you live in Stockholm, expensive city to live in.