I guess I pulled a "He's so fine/my sweet lord" on this one, forgetting I had read your suggestion. My apologies. I will update the main story. And yes, I do still wonder about how hard it is to do. As I note, it is a trade-off. It punishes certain types of people (such as illegals) that we don't intend to punish at all, and it also punishes people whom we want to encourage to reduce their gasoline use (poorer people who are forced by their poverty to live far away from work) but who can't adapt very quickly. In theory you can tune the tax and rebate to any amount and stay revenue neutral but you start making more problems at the edge.