The point is that the flow is not the same as the change in stock. If A is the stock of wealth, people tend to think that GDP is dA/dt. It is not. It is more like dA/dt + dD/dt - dW/dt + ...
These extra terms are things like increase in debt, change in mean velocity of money, usage of non-durable goods, etc. Confusing GDP for wealth flow is ignoring some of the largest factors in its calculation.
These extra terms are things like increase in debt, change in mean velocity of money, usage of non-durable goods, etc. Confusing GDP for wealth flow is ignoring some of the largest factors in its calculation.