Not as many as were predicted at first, its seems that living in Paris, having your house in Loire, is more appealing that living full time somewhere else, about 13 % of HNWIs have left.
The thing is that bugs me massively about this debate is that many of the problems the nations faces are due to this adherence to the idea that wealth trickles down. Propety prices, rising rents, public service underfunding etc can almost all in some ways be blamed on this policy.
Take for example the much celebrated HNWI diaspora to London. We celebrate this because it shows how successful London is, without acknowledging the fact that we actually get very little net benefit of this. They avoid paying taxes through non-dom status, they cause house prices to rise by buying up the most desirable properties, massively inflating the prices and causing the ripple out effect, so that areas that used to be affordable like say Queens Park suddenly become out of reach but all for the top 10 %, this of course then ripples out and means that very many workers above even the London average can't afford to get on the ladder.
Many of the purchasing taxes are avoided too, for example VAT can be reclaimed or written off against depreciation. Yet they benefit massively from living in this society.