The problem with measuring things is that once you know a thing, you can worry about it.
Also, to misquote somebody here, "There are lies, damn lies and statistics".
One could use these numbers to help national groups that seem to struggle to integrate, or you can use these numbers to discriminate.
Side note: Russia and Soviet Union are both in the graph, and Yugoslavia is on it twice as well. I guess this has to do with the fact that the numbers are collected over several years, and you can't convert one number to the other because boundaries of the countries have shifted?