Phillip Cagan (1956) hypothesized

From 1785 to 1815, U.S. shipping was subject to capture by the Barbary powers in North Africa. The U.S. government paid these powers for treaties to reduce the predation, and maintained a naval presence to protect its shipping. The Barbary powers appear to have price–discriminated in ransoming...

Federal revenues surged in the past three fiscal years, with receipts growing much faster than the economy and nearly all of the growth in the revenue due to individual income tax receipts. The 1994-7 increase in personal income tax liabilities relative to gross domestic product (GDP) resulted...