US federal prison population

Between 2015 and 2023, the US federal prison population declined while self-published books per year increased, producing an inverse correlation of -0.9656 that suggests a workforce reallocation: former inmates are becoming authors. The reality is less cinematic but the data is equally stark—one number went down, the other went up, and six data points said 'close enough.' With only six observations, this correlation has the statistical authority of a rumor, but the narrative appeal of a redemption arc. The books, presumably, are not all memoirs. But some of them definitely are.

The federal prison population declined from roughly 205,000 in 2015 to under 160,000 by 2023, driven by sentencing reform, compassionate release during COVID, and declining federal prosecution rates. Self-published books grew explosively as Amazon KDP and other platforms eliminated barriers to publication, reaching over 4 million titles annually by the early 2020s. Six data points of two trends moving in opposite directions will almost always produce a strong inverse correlation regardless of any causal connection.

Six data points is not a dataset; it is a coincidence with pretensions. The prison population and the self-published book share only a time axis and opposite directions, which is all that six data points need to produce an impressive-looking r-value.