Why do people say China is “homogenous” when people speaking Cantonese can’t understand people speaking Mandarin? It’s because those groups of people have been part of a common polity off and on since the Qin dynasty more than 2,000 years ago.

Similarly, Switzerland has been a thing, in various forms, since French and Italian were considered different dialects of vulgar Latin. The groups that speak the four different languages nonetheless share 800+ years of common political and social history.

I quite agree. It's a diversity of peoples who have developed an umbrella identity that dates back a long time. And it's been very successful!

They have a successful federal structure; much more so than more recent confederacies referred to by others in this thread (Belgium, Canada).

Absolutely agree, and of course I would never argue that "diversity" explains Switzerland's wealth. It occupied a pretty unique and interesting place during the Reformation, and maybe there is something there. But the idea that either diversity or homogeneity can explain economic performance is obviously not bourne out by any serious examples. I was thinking about Belgium (and also thinking about Harry Lime) whilst typing away--it seems a bit of a counterexample to Switzerland where the same linguistic and cultural diversity within a country can lead to very different outcomes and senses. Nobody would ever write "Il n'y a pas de Suisse" as Destrée wrote "Il n'y a pas de Belges"--long history vs short history and as always the Reformation upheavals explain it perhaps

Absolutely! Although I would have thought it was common knowledge. 62% of the Swiss population have German as their main language, 22.7% French, 8% Italian, and 0.5% Romansch. This is an extraordinary level of diversity for a European country, and as other commentators have noted it isn't like there's a lingua franca: a large proportion of Swiss do not speak the languages used by other groups fluently--for example, 85-87% of Swiss don't speak French at all!

This should be quite straightforward evidence regardless of your cultural assumptions, but many people may not be aware of the impact and cultural importance of the Reformation in Europe, which in general meant that nations ended up with a state religion that was either Catholic or Protestant. Switzerland was pretty exceptional and in the 16th Century (which is the important period here) the population was split pretty much 50/50. This religious diversity is pretty important to its history as well as to wider European history.