US national debt

The United States national debt and the number of self-published books have grown together since 2010 with a correlation of 0.9718, which raises the uncomfortable question of whether the country is dealing with its fiscal situation by writing about it.

Both the national debt and self-publishing output grew steadily through the 2010s for entirely unrelated reasons. The national debt expanded due to deficit spending. Self-published book output grew because Amazon KDP dramatically lowered the barrier to entry.

Correlating any growing quantity with the national debt is, statistically, one of the easiest things you can do. The debt goes up. Most things go up. This is not a relationship — it is a direction.