GDP: what it is, how it's calculated and what it really tells us

The economy’s odometer

When the news says “the economy grew 0.7%”, this is what they’re talking about: GDP, gross domestic product. It’s the value of all final goods and services produced within a country’s borders over a period, usually a year or a quarter. Think of it as the economy’s odometer: it won’t tell you where you’re headed or whether you’re enjoying the ride, but it tells you how fast you’re producing.

Italy, to take one national example, produced goods and services worth about €2.2 trillion in 2024 (ISTAT). A huge number that becomes manageable once you take it apart.

What goes into the count (and what doesn’t)

The key word is final. The bread sold at the supermarket enters GDP; the flour sold to the bakery doesn’t, because its value is already inside the price of the bread. Counting it twice would inflate the total.

Second rule: what matters is where production happens, not who owns it.

Practical example: a German carmaker’s plant in Italy counts in Italian GDP. The restaurant an Italian entrepreneur opens in Berlin counts in Germany’s.

Then there’s everything GDP can’t see. Pay someone to clean your house and GDP records the transaction; clean it yourself and, as far as GDP is concerned, nothing happened. Unpaid housework and volunteering: real value, statistically invisible. The shadow economy, by contrast, is in the accounts: statistical offices estimate it and fold it into GDP.

The formula: four kinds of spending

The most quoted way to compute GDP adds up what everyone spends:

Item	Who spends	Examples
C — Consumption	Households	Groceries, rent, restaurants, clothes
I — Investment	Firms	Machinery, plants, software
G — Government	The state	Schools, hospitals, public salaries
NX — Net exports	The rest of the world	Exports minus imports

GDP = C + I + G + NX. More household spending, more business investment, more public spending or more foreign demand: any of them makes the odometer climb.

Nominal vs real: the price illusion

Here GDP gets tangled with inflation. Imagine production stays identical for a year while prices rise 5%: GDP measured at current prices — the nominal one — grows 5%, yet not a single extra good was made. That’s why economists watch real GDP, scrubbed of price effects. Italy’s +0.7% in 2024 is real growth: output that actually increased.

Per capita: the right size for comparisons

Total GDP rewards big countries. To compare China with Switzerland you need GDP per capita: the total divided by population. Rankings change radically, and the number gets closer to what an “average share” looks like — while remaining an average, with all the limits averages have.

Why everyone watches it

Concrete decisions hang on GDP: governments calibrate budgets on it, central banks watch it when they move interest rates, markets react to every decimal point. And when it falls for two consecutive quarters, out comes the word nobody wants to hear: recession — at least in its “technical” version: the dedicated article explains why the serious definition asks for more.

One caveat to keep in mind: GDP measures production, not happiness. It tells you how fast the engine is running, not whether the trip is worth taking. Use it for what it is — the best odometer we have — without asking it to be the navigation system.