The Piketty and Saez data for the U.S. indicate that between 1979 and 2012, the bottom 90 percent’s income dropped by over $3,000.
But this ignores transfer income, such as Social Security. It ignores employer benefits, such as health insurance. And it ignores charges in household size over time.
When I incorporate these improvements using the Census Bureau data, I find that median post-tax and -transfer income rose by nearly $26,000 for a household of four ($13,000 for a household of one) between 1979 and 2012.