During the twentieth century, the world has become more interdependent in terms of its economics, politics, and environment. On a typical business day, about $1 trillion passes through the world's stock exchanges, while billions of dollars in goods and services are traded worldwide. People can communicate with one another globally via e-mail, fax, and the Internet. For example, a coauthor in Australia can work on an article during the day and transfer the file via the Internet, so that his or her US coauthor wakes in the morning to find the file on the computer. This enhanced interdependence is also reflected by political upheavals in one country having implications worldwide. Other examples abound. An innovative idea can be disseminated globally in a matter of days. A nuclear accident at Chernobyl dispersed a plume of radioactive material thousands of miles away, endangering much of Europe. As the carrying capacity of the planet is attained for a larger number of substances, pollutants will have a greater influence on deteriorating environmental quality at home and abroad. Now that multinational firms have become important participants in the world's economy, economic policies in one country have a greater impact on the economy of other countries. For example, more-restrictive pollution standards in a developed country can drive these multinational firms to a pollution haven in an LDC. Stock market crashes in one country create a loss of confidence in other countries' stock markets, owing to the greater economic interdependencies that arise from increased trade and capital flows.