Consider a city, paying two gardeners 25k each per year, and an extra 5k for two month. Spending is 55k+oil+chemicals+tool maintenance (that the gardeners usually do). Let's say the annualized cost is 75k. So this service contributions to GDP is 75k.
Now, the city wants to show GDP/capita growth. Simple : let's pay a company X that will pay the gardeners. It'll cost 95k. Now the GDP is 95k+ 55k (let's say the gardeners are on the same pay and have the same work). But wait, maintenance can be done by the company Y! Now the GDP is 95k+55k+20k (maintenance fixed cost 10k+worker time 7k+ 3k profit). But wait, now during winter, our gardeners have nothing to do! That eat into our profits!
Now the GDP is 95k + 50k (what is paid to the temp company)+20k+45k, and gardeners are both paid 20k/year gor this job, and can do other stuff during winter (I hear a repair shop need temp workers during inter to fix gardener tools).
The GDP grew from 75k to 160k, a bit more than 100% growth, and we optimized the economy as now gardeners can keep specializing and do gardener stuff during winter instead of learning about motors and mechanics. Great!
