One thing I've never been able to figure out is a sudden catastrophic drop in happiness. I was tooling along, with 8 happiness, healthy income, etc. Suddenly I was at unhappiness 18 one turn and 26 the next. I didn't lose any luxuries . I'm not aware of anything else happening in my civ. What the heck could have happened? This has happened before and I've never understood it. There's definitely an unknown factor in the happiness calculation, and I'd sure like to know what it is.