Only the visible gain from spending gets counted; the unseen alternative forgone is the actual cost.
Bastiat's 1850 essay: a broken window employs a glazier, but the shopkeeper's forgone shoes are invisible, and the town is a window down. It remains the standard reply to arguments that disasters stimulate economies.
In practice
- A council counts the jobs created by a stadium and never counts the businesses that did not open on the land it occupies.
- A subsidy for one industry is measured in that industry's employment, never in the workers the higher tax bill kept out of another.