Some twenty-five years ago Ada County began assessing its motorists a fee for annual emissions tests. It continues to do so, but even after all these years, those complying with the law see a portion of their assessment going to track down those who do not comply with the law. In the past five years, for example, more than 13 percent of the amount dedicated to notices and enforcement has gone to notify those not testing their vehicles that they must do so, or else.