My question might be directed more to an historian, but back in the eighties the question I was really referring to was.... If you are proposing this, I'll assume that you're not reinventing the wheel, but I also think that there was a mechanism back in the eighties to fight acid rain, a cap and trade system on sulphur dioxide, which basically was addressed through emissions or polluting rights, basically, for sulphur dioxide. These rights had a certain value, which you could compare with the value we're giving to carbon emissions at this point.
If we had that back in the eighties, how different is the current system with carbon that it necessitates those changes, and why weren't they initially used with sulphur dioxide emissions?