There are no percentile bonuses from yields anymore. The happiness system allows for constant, controlled expansion. These 2 together create this problem, since population = everything and has no limit. The happiness system is wonderful, and my only qualm is that lategame you can have tons of happiness (but then you get Golden Ages as a reward, though expanding seems to not cause much unhappiness by then). Don't change the happiness system. The lack of percentile bonuses for yields means working that yield always has the same amount of value, and that value is less than gaining more population (which gives more yields, especially with all the percentage-of-population buildings). This is what we should look at changing, imo.