GV, this is a reply to your post. I can't reply to it directly because of Yahoo's limit on the number of discussion thread branches, so I've simply replied to my own post here.
I've seen a couple of articles and news broadcasts about infidelity while in China, but they really weren't instrumental in the formation of my view regarding infidelity in China. My view stems from the University of Chicago study that I previously mentioned, a couple of other non-Chinese studies, my personal experience in China, and the stories relayed to me by other foreigners living in China.
Regarding the Chinese studies being skewed toward relatively wealthier individuals, I don't doubt that to be the case. Their methods of contacting study participants likely exclude the majority of Chinese citizens. In the case of the University of Chicago study, one can't really claim it took a truly representative sample of the Chinese population; instead, it "aimed for the middle," avoiding the both the biggest cities and the most rural areas.
Using the "sex with a non-spousal person within the last 12 months" measure of infidelity, most western countries are not too far apart. You mentioned the French. It's true that the French do tend to express relatively "open" views regarding infidelity, but when studies look at their actual behavior, their infidelity rate is on par with those of other western nations.
Culturally, I'm not sure which other country China is like; China is like China. However, high infidelity rates have also been found in some southeast Asian countries, so perhaps there are some common threads among these countries that explain this phenomenon. I do remember seeing a US study that attempted to analyze the factors contributing to the high infidelity rate in mainland China. According to the statistical analysis performed in that study, almost half of the infidelity (committed by men) took place at brothels (massage parlors and barber shops), so obviously the ubiquity of these places in China is a big factor. Another big factor indicated by the study was income disparity. There's a seemingly never-ending supply of poor individuals from the countryside migrating to the big cities. Among them are young girls who are willing to serve as mistresses for rich businessmen in exchange for financial and material support. Another factor is the permissiveness toward interactions with members of the opposite sex; obviously if it's generally regarded as socially acceptable for one's spouse to meet privately with opposite-sex friends for purposes unrelated to work and school, then more situations will arise in which infidelity can occur. The study mentioned a few other important factors, but I can't recall them at the moment.