A reader wrote to question this confusing passage from David Leonhardt’s profile of Larry Summers in the Times Magazine:

Summers’s favorite statistic these days is that, since 1979, the share of pretax income going to the top 1 percent of American households has risen by 7 percentage points, to 16 percent. Over the same span, the share of income going to the bottom 80 percent has fallen by 7 percentage points. It’s as if every household in that bottom 80 percent is writing a check for $7,000 every year and sending it to the top 1 percent.

It sounds like Leonhardt is mistakenly assuming that a change of seven percentage points in share of national income translates directly to $7,000 per household. I don’t think that’s what he means, though the passage is so opaque it’s hard to be sure. After some digging, I found that Summers mentioned these numbers in Senate testimony this year. His testimony included a table suggesting that the “net loss” in 2004 for the bottom 80% was $664 billion due to this 7 percentage point change in share of national income. If you divide that figure by the number of households in the US in the bottom 80% (approximately 90 million), you get approximately $7,000. I’ll email Leonhardt to see if this is correct.