Happiness and festivals

[pemmons1]

Festivals are really nice to have. They are encouraged by happiness in the population, but the wiki is vague about the specifics. Can anyone provide more insight?

I'm wondering especially about the happiness level of various classes of residents. The population tab in statistics shows it for each class. Is there an advantage to trying to keep the level about equal for all classes? Does the happiness of higher classes contribute more to the likelihood of festivals than that of lower classes, or is it simply based on average happiness of the entire population?

With electrification and tractors, suddenly you get overproduction of many commodities. This is a great opportunity to increase happiness by reducing working hours, even down to 50%. It took me too long to notice that this means 50% of the basic 100%, not taking enhancements into account. So if you reduce hours of an electrified factory to 50%, you still get 150% productivity. In some industries this is desirable even without the happiness bonus, because high productivity means a greater chance of fires and explosions.