Battle Nations - Population

If you touch the number on the bottom right of your screen, it will bring up the Demand window.  Demand isn't all that interesting, but this does show your population details:

There are three items to make note of:

• Max: This is the maximum population allowed for your current level.  It will typically move up by 5 or so people per level.
• Housed: This is the number of people that fit in the housing that you have built.  If this number doesn't match the Max number, then you are leaving resources on the table.  As previously discussed, Shelters house 3 and Tents house 4, both only take 5 seconds to build.  Between those two, you should always be able to come up with a cheap and quickly constructed combination of Max Pop.  The game will not allow you even start building a House that would take you over Max Pop, so you should try to hit it exactly.
• Working: This is the number of people you are actually putting to work.  If you have 3 or more people Housed that are not Working, you are leaving Gold and XP on the table.  Build a Farm and put them to work.
• Resource Depots: I put this here because I notice many people put too many population in their Resource Depots.  Your depot will max out at 100%.  The game will allow you to assign more Haulers, but it won't increase your collection rate past 100%, so there's no point.  It's just a waste of Pop.