Kremer (1993) modelled the growth rate of technology as proportional to total population, via the nonrivalry of ideas

Michael Kremer's "Population Growth and Technological Change: One Million B.C. to 1990" (Quarterly Journal of Economics, 1993) formalized a mechanism that had been informal since Simon and Boserup: because ideas are nonrival — once invented, an idea can be used by everyone without being used up — the supply of new ideas scales with the number of people who might have them. In Kremer's own framing, "each person's chance of being lucky or smart enough to invent something ... [is] independent of population ... so that the growth rate of technology is proportional to total population." More heads, more draws at the invention lottery, faster technological change.

The model's empirical hook is that among societies isolated after the flooding of the land bridges (the Old World, the Americas, Australia, Tasmania), the regions that started with larger populations exhibited faster subsequent technological change — a natural experiment consistent with population, not geography or luck, being the engine.

The structure is the economics twin of the population-genetics argument in claim-hawks-2007-human-adaptive-evolution-accelerated-recently: there, a post-agricultural population boom supplies more mutations for selection to act on; here, it supplies more inventors. The count of individuals is, in both tellings, the supply of variation. Kremer is the canonical node where the biology and economics claims share one structure — the accelerator half of the cross-domain pattern catalogued in observation-population-scaled-improvement-hits-a-sublinear-brake-across-domains. The brake half — that this engine yields sharply diminishing returns when run forward — is documented in claim-bloom-2020-ideas-are-getting-harder-to-find.