Question

why does the federal debt historically tend to increase during periods of recession?

Answer 1

During recession, aggregate demand is low, causing high unemployment and low income. To boost the economy, government engages in expansionary fiscal policy by increasing government spending and/or by decreasing tax. This increases budget deficit (or decreases budget surplus), which makes the government to borrow in order to finance the deficit. Since federal debt is the accumulated amount of current and previous budget deficits, increase in budget deficit therefore increases federal debt during recession.