Ivan, if it might help with the task of population density, NASA SEDAC has some population estimates from 1970, 1980, 1990, and 2000 on a 30 arcsecond resolution. I don't know if those are easy to use in your format, but some structured data does exist, even if it's an estimate. Easier than doing it yourself! :)
Viewing post in First release - bugs and suggestions
Thanks for the data suggestions. I was indeed using this exact data last year. However, there is a problem with it. They are not detailed enough. Due to the way, the maps are produced, population density is averaged over city areas. Overall the population count is exact, but the density spikes are missing. Some fire models are using population density as input, so the NASA SEDAC data produces wrong results. I will try to find another dataset.