During the recent economic crisis, Presidents George W. Bush and Barack Obama increased government spending by trillions, in order to revive the ailing economy. Their strategy followed the economic theory known as:

Keynesian theory

Explanation:

Keynesian theory was used by both the President of United States. President George W. Bush and as well as President Barack Obama used this theory during the crisis.

Keynesian is also known as Keynesianism, the word came from the name of economist known as John Maynard Keynes.

Keynesian theory is the theory that talks about the economics field, that for boosting the growth, the government should increase the demand.