I concur. I really favour the U.S. Clean Air Act approach that has binding consequences. Basically, if states fail to attain the national ambient air quality standard, they lose certain federal funding. The reason I favour it is we have data that it worked. We've actually seen real improvements, for example, in fine particulate matter concentrations in the non-attainment areas after these consequences were imposed.
Professor Doelle, do you want to add anything?