An OECD report shows roughly 7% of Canada's most highly educated workers living abroad. That translates to nearly 500,000 people, the 4th largest number among all OECD nations. No doubt one reason so many Canadians have left is that Canada's income tax law is territorial -- if you live outside Canada, you're not taxed on your foreign earnings.
Unlucky Americans are taxed on all their worldwide income, wherever they may live. The Canadian government is mounting a campaign to persuade Canadians who have left to come back. As a real lure, Ottawa should try cutting income taxes first.

