Singapore is a very interesting case because its multiculturalism is less organic and more top down. The upside? There are no slums. The downside? There is very little individual freedom, and punishment for crimes can be brutal. Like caning for vandalism or the death penalty for drug trafficking.
And yet! Singapore is consistently ranked as one of the happiest countries in the world. This contradicts the common western association of personal liberty correlating with happiness.
And Singapore!