the data cited by the Congressional Budget Office are based on Internal Revenue Service statistics for specific individuals and specific households over time. The IRS can follow individuals and households because it can identify the same people over time from their Social Security numbers.I don’t know if anyone else brought up the idea that the “poor quintile” is actually loaded with young people just starting out, and the “rich” quintile is loaded with mature people having a career year before Sowell did - but I don’t much care. Sowell is the one who pointed it out to me, and and as far as I’m concerned Sowell deserves the Nobel Prize.Most other data, including census data, are based on compiling statistics in a succession of time periods, without the ability to tell if the actual people in each income bracket are the same from one time period to the next. The turnover of people is substantial in all brackets — and is huge in the top one percent. Most people in that bracket are there for only one year in a decade.
All sorts of statements are made in politics and in the media as if that "top one percent" is an enduring class of people, rather than an ever-changing collection of individuals who have a spike in their income in a particular year, for one reason or another. Turnover in other income brackets is also substantial.