In Keynesian economics, consumption is the total personal consumption expeniture, or the purchase of currently produced goods and services out of income, out of savings (net worth), or from borrowed funds. It refers to that part of disposable income (income after taxes paid and payments received) that does not go to saving. Analyzing human consumption of available resources play an important role in economics, environmentalism, and geographical analysis. Consumption is generally measured by household consumption expenditures (known as personal consumption expenditures in the United States) and is determined by the consumption function, especially by the marginal propensity to consume. It is part of aggregate demand or effective demand. It can also be defined as "the selection, adoption, use, disposal and recycling of goods and services", as opposed to their design, production and marketing.