I mean, every country is unique, so different countries have different distributions of emissions in terms of where their emissions come from—some very focused on electricity, others more on transportation, others more on industrial, and so on. As a broad principle, however, because pricing of pollution is a very efficient tool that allows you to achieve emission reductions across the country, across the economy, generally speaking it's difficult to envision a comprehensive approach to reducing emissions that doesn't include it. The European Union is a good example. They have a system they put in place many years ago. That system applies more to their heavy emitters, but it's allowed for efficient emission reductions and continued reductions over time.
Our approach has generally been that you do not want to shock the system. You want to move gradually. You want to avoid a situation where you go too fast and have unintended consequences. That's why it has been beneficial to set a number, set a target, and lay out a schedule for the price. The Europeans have ratcheted down their cap very steadily over the years for quite a prolonged period without economic consequences.