[lucasjung]

"Congress and regulatory agencies are supposed to represent all the people, not just the ones that vote."

That may be what government is supposed to do, but in reality congressional representatives and senators mostly care about the ones that vote, since that's how they keep (or lose) their jobs. Also, I don't think that's all bad: "How much have you voted in the past? And do you plan to vote again next time?" is a pretty good proxy for "How much do you care about current issues?" Not voting is a way for the less informed/concerned to defer to the more informed/concerned. In an ideal world everyone would be fully informed and concerned, and so everyone would vote, but humans aren't ideal and our system handles that fact pretty well.

Furthermore, while there generally is a diffrence of about 5 points between likely voters and registered voters, and another five points between registered voters and adults, there's no way that a 1:5 ratio is going to swing the opposite way due to the difference between likely voters and the general population. At best it would shift to 1:4 or 1:3, still an overwhelming majority.