Instead of GDP he introduces SKUs (stock-keeping units) as a measure of economic complexity -> the economy is far more complex now than even relatively recently.

The economy has evolved through the interaction of three processes:

The evolution of physical technology (after the industrial revolution).
The evolution of social technology (money, markets, rule of law).
The evolution of businesses (entities that live, die, and replicate in the economic world, therefore business models are of central interest).

(Potts UQ lecture 2-3, p15)