No matter how you look at it, the past century shows substantial income gains: Between 1921 and 1971, the average income grew by $30,533; between 1971 and 2008, that increase dropped to $12,026. The difference? For that first timeframe, the richest 10% saw 30% of the growth, while 70% of gains went to 90% of the population. In the past 30 years, all the growth went to the top 10%, more than half of it to the top percentile. The data comes from economist Emmanuel Saez, and it’s widely used though often critiqued: Saez focuses on market wages and overlooks gains from government programs to help those in lower income brackets. Whether you applaud or object to his findings, they’re worth a look.