Assume that the economy is already in a recession, and both the President and Congress have decided to do something to restore the economy. Both agree that lowering taxes would not be a good idea, but do believe that it is in the best interest of the economy to increase government spending in defense, education & infrastructure.
The President and Congress change the budget accordingly, but after 18 months, GDP only increased by three quarters of the expected amount. What factors might be responsible for this situation?