Just copy and paste the below in your population.ini file. MY Location for that file is here. D:\Program Files (x86)\Steam\steamapps\common\Evil Genius\DynamicResources\Config

"MaxPopulation=300 PopulationEntry=0,300 PopulationEntry=1,300 PopulationEntry=2,300 PopulationEntry=5,300 PopulationEntry=10,300 PopulationEntry=20,300 PopulationEntry=30,300 PopulationEntry=40,300 PopulationEntry=50,300 PopulationEntry=60,300 PopulationEntry=70,300 PopulationEntry=80,300 PopulationEntry=90,300 PopulationEntry=100,300"