Some people think capitalism is wholly bad for the environment as it is based on consuming scarce resources. They want less consumption and greater reliance on renewable resources. They oppose free trade because they favor self-sufficiency (autarky), or at least so-called fair trade, and because they believe it encourages poorer countries to destroy their natural resources in order to get rich quick. Although few professional economists would share these views, in recent years many attempts have been made to incorporate environmental concerns within mainstream economics. The traditional measure of GDP incorporates only those things that are paid for; this may include things that reduce the overall quality of life, including harming the environment. For instance, cleaning up an oil spill will increase GDP if people are paid for the clean-up. Attempts have been made to devise an alternative environmentally friendly measure of national income, but so far progress has been limited. At the very least, traditional economists increasingly agree that maximizing GDP growth does not necessarily equal maximizing social welfare. Much of the damage done to the environment may be a result of externalities. An externality can arise when people engaged in economic activity do not have to take into account the full costs of what they are doing. For instance, car drivers do not have to bear the full cost of making their contribution to global warming, even though their actions may one day impose a huge financial burden on society. One way to reduce externalities is to tax them, say, through a fuel tax. Another is prohibition, say, limiting car drivers to one gallon of fuel per week. This could result in black markets, however. Allowing trade in pollution rights may encourage “efficient pollution”, with the pollution permits ending up in the hands of those for which pollution has the greatest economic upside. As this would still allow some environmental destruction, it might be unpopular with extreme greens. There may be a case for international eco markets. For instance, people in rich countries might pay people in poor countries to stop doing activities that do environmental damage outside the poor countries, or that rich people disapprove of, such as chopping down the rain forests. Choices on environmental policy, notably on measures to reduce the threat of global warming, involve costs today with benefits delayed until the distant future. How are these choices to be made? Traditional cost-benefit analysis does not help much. In measuring costs and benefits in the far distant future, two main things seem to intervene and spoil the conventional calculations. One is uncertainty. We know nothing about what the state of the world will be in 2200. The other is how much people today are willing to pay in order to raise the welfare of others who are so remote that they can barely be imagined, yet who seem likely to be much better off materially than people today. Some economists take the view that the welfare of each future generation should be given the same weight in the analysis as the welfare of today’s. This implies that a much lower discount rate should be used than the one appropriate for short-term projects. Another option is to use a high discount rate for costs and benefits arising during the first 30 or so years, then a lower rate or rates for more distant periods. Many studies by economists and psychologists have found that people do in fact discount the distant future at lower rates than they apply to the near future.