This is why Paradox's game design was flawed in that Population wasn't factored in. You COULD have Novgorod properly subordinated, but Novgorod's population would reflect the reality of that time - sparsely populated areas without much contribution to the Economy or military/manpower. To me, this is a core argument for the future EU5 build, that we should see more significant differences in population "volume" by provinces and regions of the world, but enable colonization to push the population growth up, perhaps in spikes also (pop-up events, in theory, could be built in).