there was a strong correlation between the number of parking tickets issued to diplomats from a country and independent measures of corruption in that country,

there was a strong correlation between the number of parking tickets issued to diplomats from a country and independent measures of corruption in that country, showing that the norms really were an important part, and carried over even into a different environment. That makes sense, in the same way that you'll find that Americans tend to tip even in countries where tipping is not customary. The real question is how did those cultural norms start in the first place?