One of the largest single reverse migrations was that of New England Puritans who returned to England in the 1640s.

It has been estimated that 7% - 11% of the population of New England returned to England in this period.

Source: Susan Hardman Moore, "Pilgrims, New World settlers and the Call of Home", 2007

That might have been as many as 3,000 people.

The reason for this return, of course, was the outbreak of the English Civil War. The Puritans had gone to New England to build a new religious life un-surrounded by the troublesome non-puritan majority in England.

Suddenly, it looked like the Parliamentarian side might be going to achieve a Puritan nation in civilized England, rather than in the howling wilderness. Many Puritans returned to England to join the fight.

Of course, they were ultimately disillusioned. Rather than a libertarian Puritan paradise, they got a military dictatorship by Oliver Cromwell, and ultimately a return to Monarchy and the established church.

The English Civil War had a large and lasting effect on American thought and history. It is unfortunate that it is not studied more in the USA as part of the shaping of the American Revolution.