See if your current houses are full, click on any of your market places. On the bottom left of the window that pops up there is a second tab, but it might be a good idea to deny accension rights to better control your population, you can do that from the first tab, at the very top click the scroll. Moving onto the second tab, this shows a bar chart of the number people and their classes currently in your settlemen. If you hold your mouse over one of the bars, for example citizens, it will show you a fraction like 189/240. Shows that you still have space left to fill.
To fill this space you have to change the tax level, click on a house belonging to the class you would like to change the tax level for, citizens in this example. Theres 5 different levels of tax, these bars shift along depending on how your settlers needs are fullfilled. You want to move your tax level to light green, this makes your settlement more appealing to the citizens and makes them start to move in and fill up your empty house spaces.
Quick rundown of how each tax level effects your settlers:
Level 1, Dark Green - Settlers move in and wish to accend to the next level if all their needs are fulfilled.
Level 2, Light Green - Settlers move in but dont want to accend.
Level 3, Yellow - Settlers dont move in but they dont move out.
Level 4, Orange - Settlers move out :'(.
Level 5, Red - Settlers go on a witch hunt and try to kick your face in.
Also a note on advancing to quickly, say you have your settlement up to the citizen level, everyones needs are met and your houses are full, your taxing them at level 3 and making a nice profit. Your ready to upgrade to patricians. Now if you just let everyone advance right away you will be stuck with aload of patricians whos needs are not met and are not paying as much taxes as the citizens. So upgrade one or two houses just to unlock the first few buildings the next level needs. This way you can go off and build them, in this case its wheat, mill and bakery for bread. Once you have this setup then you build more patricians houses to unlock the next set of buildings. With the bread they are alightly more happy and willing to pay more taxes, less of a problem on your wallet.
