The crop yeilds are too low or the people eat too much. I stuggle after 40 people with keeping them from starving. On the easiest settings, no disasters and "mild" climate (not mild by the way!) I still can't manage it. There are too many jobs needed as your population gets bigger, but even when I dedicate most to farming I still come up short. I think the solution is that crops should just yeild a lot more. 25% to 50% more at least. I also think after 40 no matter how close I place things villagers start to suck as doing their jobs....