C + I + G + (X − M) = 21,000, and the last bracket is negative here
The expenditure approach counts everything bought in final form: 14,000 of household consumption, 4,000 of investment, 4,000 of government spending, and net exports of 3,000 less 4,000 — a trade deficit of 1,000. The total is 21,000, and in the default figures those units are billions of dollars, roughly the scale of the United States.
Consumption dominates in most developed economies, typically two-thirds of output, which is why consumer confidence surveys move forecasts so much. Imports are subtracted not because trade is harmful but because they were already counted inside the other three: a household buying an imported car adds to consumption, and the subtraction removes output that was produced abroad.
The −1,000 here is an accounting subtraction, not a verdict
Net exports enter GDP as a single signed figure, so a country importing more than it exports reduces the total. That is arithmetic about where goods were produced, not a judgement about the economy. A deficit usually accompanies strong domestic demand — households wealthy enough to buy from abroad — and often sits alongside a capital account surplus as foreign money flows in the other direction.
It does mean the headline figure understates domestic consumption. An economy with 21,000 of GDP and a 1,000 deficit absorbed 22,000 of goods and services; it simply produced 1,000 of that elsewhere. That distinction matters when comparing living standards, where consumption per head is often more informative than output per head.
Expenditure, income and production must agree, and in practice never quite do
GDP can be measured by what was spent, by what was earned as wages, profits, rent and interest, or by the value added at each stage of production. In theory the three are identical, because every dollar spent is a dollar earned. In practice national statistics offices publish a statistical discrepancy, usually well under 1% of output, because the three are built from different surveys.
This calculator uses the expenditure method, which is the one most published data follows and the easiest to build from observable spending. Where you see a headline figure revised months later, it is usually the reconciliation between the three approaches working through, and revisions of half a percentage point on quarterly figures are entirely routine.
Unpaid work, environmental cost and everything informal
GDP measures market transactions in final goods. It therefore excludes unpaid household work and caring, which is a substantial share of real economic activity and is distributed very unevenly; the informal and cash economy, which in some countries exceeds a third of measured output; and any depletion of natural capital, so an economy cutting down its forests records the timber as output and the loss as nothing.
It also says nothing about distribution. Two economies with identical GDP per head can have completely different median incomes. None of this makes GDP a bad measure of what it measures — the volume of market production — but it makes it a poor single measure of welfare, which is what supplementary indicators such as the Human Development Index exist to address.
One period, nominal figures, and consistent units
Every input must cover the same period and be measured in the same units — mixing a quarterly investment figure with annual consumption produces a number that means nothing. The result is nominal unless the components entered were already inflation-adjusted; to get real GDP, deflate by a price index first, or use the GDP deflator page to convert between the two.
Intermediate goods must be excluded or output is double-counted: the steel in a car is already inside the car\u2019s price. Second-hand sales are excluded too, since the item was counted when first produced. For published data, these adjustments are already made — this calculator assumes your inputs are final-demand figures.
Sources & References
Figures on this page are checked against primary, authoritative sources. Links open in a new tab.