Many people are interested in the distribution of income and wealth and how it may have changed over time. But there is no single and undisputed source for such data. Rather, economists construct historical time series using partial information and many assumptions.

French economist Thomas Piketty and colleagues have for years been publishing data showing extreme changes in top 1% income and wealth shares in the United States over the decades. Many news outlets report the information unquestioned, despite evidence that Piketty is sloppy with data and makes bad assumptions that throw his calculations off.