In France at least: amount of freight, sqm of new buildings, industrial production, primary energy consumption, etc, basically all the physical things you can actually measure, etc.

Then you add in "services" and "assets growth" to cook the numbers (don't forget to incldue illegal drug trafficking and illegal prostitutions numbers to jack things up even more even though you have no real data about it), and magically everything in the the green, although pensions are decreasing, retirement age is increasing, social benefits are being cut left and right, but don't worry brother, we're in the green!