Normal for Save to keep increasing player counts?

So I started a save at about 100,000 players just to simulate games. Now it is 15 years in and the player count is at 157,000. I thought the game try to keep the player counts at around what you started at.  Is that normal to keep having players increasing each year? I'm trying to get to 100 years simulation. By this count it will be way over 200,000 players soon.