I'm not entirely sure what you mean, since immigrants would tend to have a lower income level, But I think my answer is yes, if you factor out middle-to-high i

I'm not entirely sure what you mean, since immigrants would tend to have a lower income level, But I think my answer is yes, if you factor out middle-to-high income rioters, you would still see a disproportionate representation of immigrants to natives. My theory is fairly simple: it's about incomplete integration. If natives fail to identify immigrants as accepted natives, there will be conflicts that regularly break out into anything from racial profiling to riots (such as the famous LA riots) to civil wars to secessions (such as South Sudan). I could also be completely crazy in seeing this pattern, though; I'm not an expert in this area by any means.