What Is GDP?

The Size of the Economy

GDP adds up the market value of everything an economy produces, goods, services, investment and more, over a quarter or a year. On its own the headline figure is enormous and abstract; what actually matters is the growth rate, whether GDP is rising or falling and how fast. That growth rate is the single most-watched summary of an economy’s health, the number politicians campaign on and central banks steer by.

How GDP Is Calculated

The most common method adds up everything the economy spends, captured in a simple formula: GDP equals consumption plus investment plus government spending plus net exports, often written C plus I plus G plus NX.

• C, consumption. Household spending on everything from groceries to haircuts. In most rich economies this is the largest slice by far.
• I, investment. Business spending on equipment and buildings, plus new housing.
• G, government spending. Public spending on goods and services, from roads to salaries.
• NX, net exports. Exports minus imports, so a country that imports more than it exports has a negative contribution here.

Nominal Versus Real GDP

This distinction trips up almost everyone, and it matters enormously. Nominal GDP is measured at current prices, so it rises both when an economy produces more and simply when prices go up. Real GDP strips out that price effect using an adjustment called the deflator, leaving only the genuine change in the quantity of stuff produced. If nominal GDP grew 5% but prices rose 3%, real growth was only about 2%. When economists talk about "growth", they almost always mean real GDP, because that is the part that reflects a richer, more productive economy rather than just a more expensive one.

GDP Growth and Recession

The growth rate of real GDP is the headline gauge of economic health: rising is good, falling is bad. The widely repeated rule of thumb is that two consecutive quarters of negative real GDP growth count as a recession. It is a useful shorthand, but only a shorthand: in the US, the official call is made by the National Bureau of Economic Research, which weighs employment, income and spending too, and can declare a recession that does not fit the neat two-quarter rule, or decline to call one that does.

What GDP Doesn’t Measure

For all its power, GDP is a famously incomplete picture, and knowing its blind spots is part of using it well.

• Distribution. It measures the size of the pie, not how it is sliced, so strong growth can mask deepening inequality.
• Unpaid and informal work. Care done at home, volunteering and the black market are largely uncounted.
• Wellbeing. Health, leisure, education quality and the environment do not show up, and pollution can even raise GDP.
• Depreciation. The "gross" in GDP means it ignores the wear and tear on the machines and buildings doing the producing.

This is why analysts pair GDP with other measures, like GDP per person, to judge how an economy is really doing for the people in it.

Why Markets Care

A growing economy generally means growing company earnings, which supports stocks and confidence, while shrinking GDP signals trouble for both. As with most data, markets trade the surprise, the gap between the GDP figure and what economists expected, more than the raw number. The catch is that GDP is deeply backward-looking, reported weeks after the quarter it covers and revised more than once afterwards, so by the time it confirms a slowdown, markets, which look forward, have usually moved already.

GDP, Growth and Sentiment

Because GDP arrives late, sentiment often turns first. The crowd starts to feel a slowdown, or a recovery, before the official numbers confirm it, which is why a live Fear and Greed Index can lead the hard data. Reading a GDP release alongside where sentiment already sits, on the same 0 to 100 scale, tells you not just how the economy did, but how much of that was already expected and priced in by a forward-looking market.