Do stock market gains help drive rising income tax receipts?
Core argument: Inflation-adjusted 12-month U.S. individual income tax revenue stands $567 billion above its level just before the pandemic, with the 2021–2022 inflation wave a big contributing factor in the rise in receipts.
The inflation wave of 2021 and 2022 was a big contributing factor [in the rise in income tax receipts], but after adjusting for inflation, 12-month individual income tax revenue is still $567 billion higher than just before the pandemic. Movements in US individual income tax receipts follow movements in the Standard & Poor’s 500 Index. The correlation is strongest with a 10-month lag. The r-squared is 0.49, meaning that the change in the S&P 500 “explains” almost half the change 10 months later in trailing-12-month individual income tax receipts — although of course the causality is probably more complicated than that. With the S&P 500 hitting a record last week, that should mean income tax receipts will keep rising for 10 more months. But after gaining 24% in 2023, 23% in 2024 and 16% so far this year, the S&P is also due for a sustained pullback one of these days — which would make it much harder to keep shrinking the deficit.

