The Rich Have Stayed Rich in England for 1,000 Years

Something tells me that this isn't the full story.

While it may be true that the top 1% of British society has remained constant for 1000 years, Britain's place within the world power system has changed dramatically. They went from a sleepy backwater island during the Dark Ages, to a major European power under Elizabeth I, to the pre-eminent global power during the British Empire, to a sleepy backwater island as the U.S. ascended after WW2. It's telling that the article eventually turns to "But what does this mean for America, the land of opportunity?"

It's also telling that of the three families highlighted - Rockefeller, Vanderbilt, and Kennedy - Cornelius Vanderbilt's great-great-grandfather emigrated to America as an indentured servant, John D. Rockefeller was the son of a con artist, and JFK's great-grandfather was an orphan who emigrated from Ireland to avoid starvation.

I think a more accurate lesson might be that social mobility within an established social hierarchy is impossible. You have to transcend the existing social structure, basically leaving your existing place in society to join a different society that's growing much faster.