How do I increase my idle population?
In order to increase your idle population, follow these simple steps:
Lower your tax rate. Happier people means a higher idle population
Build more Homes, or upgrade existing ones. Homes in Outposts contribute to your total idle population. The more room for people you have, the more room you have for an idle population
Build or upgrade your Theater. The happiness bonus provided by your Theater allows for you to raise the Tax level even higher without negatively affecting your population
Use a Nomadic Recruits item. Using this item will allow you to temporarily boost your Idle Population by 20,000
Please note that Lumbermills, Mines, and Quarries all use up your idle population. As you add more of these buildings your idle population will decrease.
Troops also use up your idle population, so be sure to follow the steps above before training a large quantity of troops.