I'm fully supportive of an approach of having people make a pledge, demonstrate some service commitment once on US soil if they intend to stay. Heck, I'm actually ok with something like Australia's approach. But in the end, there simply is no guarantee of allegiance. As for those who vote and basically only have their own personal interest in mind, well I'm not sure that your stated percentage is high enough, regardless of political affiliation. As for trying to determine who and who not to let in this country, it is a difficult slope because regardless of what they say, they may have other motives.