Suppose you are given data about the population of a country from say 1800 to 2010. You are also given some explanatory variables regarding migrations to that country, inflation rate, and other socioeconomic factors. The goal is to predict the country's population for the next 100 years. Is there any literature about population growth models because it seems that a simple linear regression model will not suffice. Would a deterministic model be better in this case? I have also tried time series methods, but it seems that simple differencing, or log transforms do not make the series stationary meaning that I cannot build an ARIMA model. I'm looking to building an interpretable model.