When there is a shock to the economy, it is generally thought to have a multiplied effect on the economy. Some households enjoy higher income, they spend it, increasing the income for other households, who in turn spend it, and so on. The size of the multiplier is finite because there are leakages: some of the increase in income may be saved, used to pay taxes, or used to buy imports, and is therefore not available as income to others.
How big are these multipliers? Menzie Chinn provides some estimates at Econbrowser.