Per capital growth is also not sufficient. Such a metric could easily be achieved by slowly reducing the population to 1. I might propose some analog of total output minus population growth as a better metric.
> Per capital growth is also not sufficient. Such a metric could easily be achieved by slowly reducing the population to 1
Only if the 1 person can continue to increase their productivity with nobody else to trade with, which is absurd. Increasing productivity comes from specialization and trade.
The article talks about "growth" as though it has to be absolute growth, but it doesn't; it only needs to be per capita growth. If the population is shrinking, absolute growth can be negative but per capita growth can still be positive (all that's necessary is that the rate of absolute decline of the economy is less than the rate of decline of population). In other words, per capita productivity just needs to increase. Which it has been at least since the industrial revolution.