UCCLE, Belgium – The 8,500 French residents of this affluent Brussels suburb count the Taittingers, of champagne fame, among their well-heeled neighbors. France’s richest man, luxury-goods mogul Bernard Arnault, is shopping for some high-end real estate here too.

Sure, the patisseries, chocolatiers, trendy boutiques and assurance that Paris lies a short train ride away make the emigres feel right at home. But for the mega-rich among their number, there’s another draw: More of their vast fortunes stays in their pockets and out of the taxman’s.

Last month, the Socialist government of French President Francois Hollande decided to increase its take on earnings above $1.3 million to an eye-popping 75 percent, a “supertax” that has dismayed those who have to pay it and delighted those who don’t. By contrast, Belgium’s top income tax rate is 50 percent.