I honestly believe that it's not a function of how much technology there is (and exponential growth based on that), but on number of
technologists or
inventors available to develop new technology. That, in turn is a function of the number of people in the society and the ability to educate them in the ways of technology. Roughly speaking, it
seems like technology builds on itself in its own growth, but that's because:
- (a) improved technology has led to advancement in education (both technologically as with the printing press) and culturally as education came to be viewed as an important means for the society as a whole and not just the elites; and
- (b) as technology has advanced, population has been growing at roughly a similar rate.
The increase in the rate of technological advancement and relationship with the existing stock of technology is, in my opinion, a case where "correlation doesn't imply causation " becomes important. If a world wide plague wiped out 80% of the human race tomorrow, I'd expect to see a crash in the rate of technological development, notwithstanding the fact that the stock of existing technology remained unchanged.