When Bush was campaigning, the media refused to consider the immigrant situation in Texas when it came to education statistics and poverty levels. It obviously makes a huge impact on states with high immigration levels unless you're a Republican running for office.
Umm, it means that the immigrants are probably INCREASING their median incomes, so it is not a downer for them. And it DOESN'T mean you whitey's are declining in your incomes, so it is not a downer for you.
This is one of those statistics that is actually saying something quite different than the great unwashed think it says. But ya know, gotta hate those wet backs -- can't have logic get in the way.