While I agree with your sentiments on a lack of proper data, there is another hypothesis for foreign students, perhaps having a higher rate of cheating. One that is not bigoted at all, and applies equally well to a subset of north american students.
Some cultures, India, China, perhaps others, currently place immense value on education. This brings with it immense pressure. While that can lead to a good work ethic, perhaps the immense pressure can also lead to a higher likelihood of cheating. It's not that these students underestimate the risk of getting caught, but more that they may be more afraid of the reaction of their family or peers back home if they fail.
Getting good grades is not exclusively a result of hard work. Often it can be genuinely challenging. For some international students, failing can mean a loss of scholar ship and thus having to leave back home. For students in China, for example, this may mean a loss of freedom, and certainly a big loss of social rank back home.
North American students studying here may occasionally have a lot of pressure from home, but they never risk being denied citizenship, or being relegated to low paying jobs for the rest of their life with no chance of improving.
In some graduate programs, this fact is occasionally taken advantage of by unethical professors, who can get away with treating their international students poorly.
I had a professor from France this semester. He went on a tirade about how we should cover our papers and not cheat. The whole class(all Americans) seemed pretty lost and could not relate to his lecture on cheating. I see a similar response when mainly foreign professors ask students to switch seats and spread around the room on exam days.
My French professor said when he went to college in the US, he had moments where the professor left the class and my professor(then a student) would look around him hoping folks would "cooperate"(in funny French accent). I'm not sure how much of that was said as a joke but I think the sentiment has at least some truth to it.
I can definitely tell you that while I was in India and my initial few years in the US, I was under immense pressure to perform. That is also when I would be most inclined to do not-so-ethical things. Then over time the pressure goes away and the incentive to cheat does not seem greater than just doing the work or accepting a poor grade.
Some cultures, India, China, perhaps others, currently place immense value on education. This brings with it immense pressure. While that can lead to a good work ethic, perhaps the immense pressure can also lead to a higher likelihood of cheating. It's not that these students underestimate the risk of getting caught, but more that they may be more afraid of the reaction of their family or peers back home if they fail.
Getting good grades is not exclusively a result of hard work. Often it can be genuinely challenging. For some international students, failing can mean a loss of scholar ship and thus having to leave back home. For students in China, for example, this may mean a loss of freedom, and certainly a big loss of social rank back home.
North American students studying here may occasionally have a lot of pressure from home, but they never risk being denied citizenship, or being relegated to low paying jobs for the rest of their life with no chance of improving.
In some graduate programs, this fact is occasionally taken advantage of by unethical professors, who can get away with treating their international students poorly.