Umfairteilen, whose name plays on the German word for "redistribution," advocates a one-time tax and an annual levy. But there's little indication that the conservative government of Chancellor Angela Merkel is on board.
"You still have a lot of people in Germany believing what Angela Merkel and the liberals say, that there will be more wealth and happiness if you have the rich and do not ask them to give more," Sundermann says. "But there is some change."
In Spain, the newly installed center-right government pledged to repeal the wealth tax that its Socialist predecessor instituted. But with debt levels rising, putting Madrid at the center of fresh fears over the euro crisis, the ruling party has had to abandon that vow. Spaniards with assets exceeding $900,000 must continue coughing up an extra 0.2 percent to 2.5 percent to the state.
Iceland also adopted a wealth tax after its economy tanked during the global financial meltdown. On the other hand, the Swedes ditched theirs in 2007 because officials said it encouraged residents such as Ikea tycoon Ingvar Kamprad to park vast amounts of capital offshore instead of investing it in Sweden and creating jobs.
In Britain, which is straining to put a brake on its runaway deficit, the junior governing party has called for a "mansion tax" on properties worth more than $3.2 million.
"I think the public wants to make sure the country balances its books in the fairest possible way," says lawmaker Stephen Williams of the Liberal Democrats. "I think the public would want to see people on higher incomes and greater wealth contribute their fair share."
Prime Minister David Cameron and his Conservative Party have ruled out the mansion tax proposal, fueling tension between the coalition partners.
Still, Cameron has felt compelled to join, at least rhetorically, in the rising clamor for the well-off to give more. "The richest in our country have to make a contribution in what is a national effort to reduce our deficit and get our country back on track," Cameron told BBC Radio.
Here in Belgium, more than a tenth of Uccle's population is French. When Arnault, whose LVMH empire includes Louis Vuitton and Bulgari, confirmed his intention to seek dual French-Belgian citizenship, one of France's leading papers splashed the headline "Get lost, rich jerk!" on its front page.
Arnault insists he'll continue to pay French taxes. He says his move to Uccle is purely to expedite investment projects he has planned in Belgium, though critics point out that Belgian citizenship isn't necessary for that.
De Decker, the mayor, recalls that Arnault said nothing about trying to avoid France's super-tax when the two met late last year but that he did complain about widespread hostility at home toward wealthy people.
De Decker says Arnault told him: "In France, they don't like entrepreneurs. They don't like successful businesses. They hate success. It's a jealous nation.
"And if they are still going like that, I prefer to come to Belgium."