Why are highly-skilled Britons and Western Europeans leaving for the U.S.?

The new OECD report shows a brain gain for Britain: 1.26 million immigrants live in the country, but 1.1 million immigrants left, which gives a net "brain gain" of more than 100,000 people.

Here's what the article doesn't say: these immigrants are disproportionately coming from the third-world. In fact, all Western European countries are losing their own skilled workers and trying to replace them with third-world workers.

Where are the British and Western European workers going? To the U.S. of course. The same OECD report noted that the US was the only country to receive more highly-skilled immigrants from OECD countries than it lost. It had a positive balance of about 1m highly-skilled migrants from the EU 15 (pre-2004-accession)