If the marginal propensity to consume were 100 percent, there would be no investment, and, soon, no income.

FORBES: The Flawed Assumption Behind Ending The Bush Tax Cut For The Rich

Those in upper-income groups with incomes above a million dollars a year tend to have a lower marginal propensity to consume.

WHITEHOUSE: Press Briefing

You could compute a multiplier, which was simply the reciprocal of one minus the marginal propensity to consume, or, even more simply, the reciprocal of the marginal propensity to save.

FORBES: The Flawed Assumption Behind Ending The Bush Tax Cut For The Rich

To the extent that high oil prices played a role in the recessions of the early 1980s and 2008-09, the main reason is that oil-producing countries tend to have a lower marginal propensity to consume their income, denting global demand.

ECONOMIST: The economic impact of high oil prices