I'm a bachelor student writing a paper on the effects of China's one child policy on future GDP. My professor told me to use growth models. However, I'm unsure which growth model I need to use for this kind of research. I'm only familiar with the Solow model and two-sector models that expands on the Solow model by introducing an R&D sector (I've seen these in their most basic form in one of my classes).
Since a major effect of the policy is a decreasing workforce, I think that technological progress (knowledge accumulation) and population growth are important, but a lot of models seem to hold population growth constant?