The Root Cause of U.S. Debt People say the government has a debt problem. Debt is caused by deficits, which is the difference between what the government collects in tax revenue and the amount of government spending. Every time the government runs a deficit, the government debt increases. So what's to blame: too much spending, or too little tax revenue? Economics professor Antony Davies examines the data and presents his conclusion. Spoiler Alert: the root cause of the debt is too much government spending. (Back to Video)