Since there are currently zero benefits to population, I recommend that population should increase tech by a nominal amount. As mathematically speaking, the more people that are born, the greater chance there is for a genius to be born.
I would say an increase in productivity instead, due to greater economies of scale.
There are many missing effects of population in the game, such as modifying GDP → Environment and GDP:debt. You can add “economies of scale” to this list, which is definitely a productivity factor.
I’m not so sure about technology. If population was all you needed for technology, India would have become a superpower in 2020. As it stands now, India’s high end human capital emigrates. China remains not very technologically productive on a per-capita basis.
Well, I don’t mean there has to be a 100% link. It could be 1-5%.
Hmm…I guess, that’s also a case to be considered.