Consumption and investment are the two components of aggregate demand in a simple two-sector macroeconomic model that assumes no government or foreign trade. Consumption is determined by disposable income and other factors, while savings is the portion of disposable income not consumed. The marginal propensity to consume measures how consumption changes with income, and is between 0 and 1. Determinants of consumption and savings include income, interest rates, prices, wealth, and demographic factors.