[Gen.Blather]

I couldn’t get to the article, but I believe these are mostly people who have US citizenship but are living and working in other countries. The tax laws have become so complex and dangerous that they have opted to drop citizenship rather than risk the IRS coming after them for taxes it has declared it is owed.

[skeeter]

I’d bet most of them were at one time immigrants here themselves. They have a place they can comfortably relocate.

[Brandybux]

"I couldn’t get to the article ..."

Here's how you get to the article without a subscription (at least for a few days, before the procedure itemized below generates a broken link):

• Copy the aricle's headline to your computer's clipboard. This needs to be accurate.
• Navigate to Google News.
• In the search field at the top of the page, paste the article's headline from your computer's clipboard; then either hit the RETURN key or click on the blue button at the right end of the search field.
• The article you're seeking is at the top of the resulting list of results for the search. Click on that link.
• Viola!

This also works with the Financial Times, though that site may ask you to answer an inane question first.