 I got my degree in 1987 then I worked for the government. I've been teaching this class since 1991, so for about 18 years. And the classes changed, and in particular what's changed is society has become richer and become more interested in environmental issues. And also, and this is something I would not have predicted 10 years ago, energy issues have become environmental issues. All energy issues now have environmental components. You want to build a new gas plant, that emits certain problems. You want to build a natural gas plant, you want to build a coal plant, you want to build a nuclear power plant. All those have different types of environmental features. And so, for me, what I've seen in the course of teaching this is that the environment has become much more important to society. And from a policy point of view, much more interesting. What you see in developing countries is people who struggle for food don't have the luxury of worrying about clean air. And that as societies become richer, people become more financially secure, they live longer, they're more concerned about health issues, they're more concerned about the environment. And they're more able, by the way, to engage in environmental goods, to engage in tourism, to go see things that are interesting from environmental point of view. And so all this implies that a richer society will care more about the environment. And for me, of course, the reverse is also true that a poorer society will not care about the environment. And actually, one way to protect the environment is to generate incentives and systems to cause societies to become richer. And so they'll be more interested in protecting the environment. Well, interesting is you see countries get richer, they become more interested. So currently, China and India are becoming richer. And you see a larger interest in environmental issues there, particularly China and industrialization has had terrible air pollution problems. And finally, the government there is starting to respond to that. On the other hand, Russia, which has really had tremendous economic difficulties, does not seem so interested in environmental issues, even though they had tremendous environmental issues dating from the communist era, where the government really didn't care about protecting the environment and nobody had any incentives to protect the environment. So they had some real environmental horror stories. Today, they're still struggling. They seem less interested in the environment. Western Europe, which has become richer, continues to be interested in the environment. The United States has become richer. And this is an interesting trend.