If economics was a science, and if economists paid any attention at all to the basic laws of physics and to what they might say about the size of the world economic system then they would realise that, sooner or later, it’s fixed. It may oscillate a little about an average level of activity but, to all intents and purposes it won’t alter — unless some amazing new, and very large, source of energy can be somehow injected into the system. This is called the Law, or Principle, of Least Effort. It’s when all of the variable factors within the system — some pushing it forward, some holding the system back — are in balance.
It’s therefore nonsensical to talk of a growing world economy — apart from temporary surges — because we don’t know where our present one is at. It may be less than it might ultimately be. On the other hand, it may already be too large. We just don’t know at present because the industrial revolution, which started with a bang in Manchester at around 1780, is still far from played out in the advanced countries. We have yet to see the characteristics of a service economy when automation has gone as far as it can.