Aggregate income is the total of all incomes in an economy without adjustments for inflation, taxation, or types of double counting. Aggregate income is a form of GDP that is equal to Consumption expenditure plus net profits. 'Aggregate income' in economics is a broad conceptual term. It may express the proceeds from total output in the economy for producers of that output. There are a number of ways to measure aggregate income, but GDP is one of the best known and most widely used.

GDP stands for gross domestic product. GDP is a measure of the economic output of a country. It is usually defined as the total market value of goods and services produced within a given period after deducting the cost of goods and services used up in the process of production, but before allowances for depreciation. Most countries compile estimates of their GDP based on guidelines from the United Nations.

GDP (Y) is the sum of consumption (C), investment (I), government spending (G) and net exports (X – M).

Y = C + I + G + (X − M)

Here is a description of each GDP component:

C (consumption) is normally the largest GDP component in the economy, consisting of private (household final consumption expenditure) in the economy. These personal expenditures fall under one of the following categories: durable goods, non-durable goods, and services. Examples include food, rent, jewelry, gasoline, and medical expenses but does not include the purchase of new housing.

I (investment) includes, for instance, business investment in equipment, but does not include exchanges of existing assets. Examples include construction of a new mine, purchase of software, or purchase of machinery and equipment for a factory. Spending by households (not government) on new houses is also included in investment. In contrast to its colloquial meaning, "investment" in GDP does not mean purchases of financial products. Buying financial products is classed as 'saving', as opposed to investment. This avoids double-counting: if one buys shares in a company, and the company uses the money received to buy plant, equipment, etc., the amount will be counted toward GDP when the company spends the money on those things; to also count it when one gives it to the company would be to count two times an amount that only corresponds to one group of products. Buying bonds or company shares is a swapping of deeds, a transfer of claims on future production, not directly an expenditure on products.

G (government spending) is the sum of government expenditures on final goods and services. It includes salaries of public servants, purchases of weapons for the military and any investment expenditure by a government. It does not include any transfer payments, such as social security or unemployment benefits.