Fictional Populations

It only recently occurred to me that I should figure out the country populations in my world. 

As usual, it ended up being more complicated than I expected. I thought I'd make the populations somewhat similar between countries, since they're similar sizes. Though of course some lands can support more people than others. There are some countries that are mostly desert or tundra. 

I decided to start with the country I'm working with most right now. I looked into the original populations of that area of the US before Europeans arrived. Which brought the first hurdle. No one actually knows the original populations. Europeans didn't bother to find out how many American Indians there were before they started killing them and spreading disease (and the disease sometimes arrived before the Europeans did). The estimated population for the area ranges between 100,000 and 700,000. So it's not too helpful. It's a very fertile area of America, so there were many more people living there than in some other areas. I decided to go with the higher population estimate, and maybe a bit higher. 

One of the main reasons I needed to know the population was to figure out the number of mages, and how many people might use the mage temple. 

Long ago, I decided that about 1% of the population has magic. But not all of those people would go to the temples to learn. I'm not sure if that number would include genetic magic - those people mostly learn magic from their communities, not from temples. Some mages would have magic that's so insubstantial that they wouldn't really need training at the temple. And some mages would get trained privately (for various reasons). 

So, I have a ball-park idea for the population, and the number of mages. But it still needs work.