Why do people change their opinions about what sorts of problems are important years after year?
Currently, very few people tell pollsters that the environment is a top concerns for them, but this has not always been the case. In 2000, a high percentage of people claimed to be worried about the environment, but not now. What's changed is the economy. When the economy does well, people tend to worry about other things - like the environment. When it isn't, the more immediate pressing concerns drive out those that won't materialize until sometime in the future.
