That is how Alfred Marshall, the great 19th century economist, defined economics in his classic textbook, Principles of Economics. The text you have in your hand continues that tradition, from the cover image to the last page. The cover of this and previous editions shows a market scene. It reminds us that economics is about people as they go about their lives. Economics is about buying, selling, setting prices, competing for customers, looking for jobs, and earning a living. It is about why markets so often succeed as a way to run a society and why they sometimes fail. When the Mankiw text was first published, The Economist wrote, "Mr. Mankiw's book sets a new standard for clarity and liveliness." USA Today called it "a grand success." Since then, the book has indeed become the new standard for introducing economics to students like you around the world. It has been translated into twenty languages, and more than a million copies have been sold. Thomson South-Western is pleased to bring you this Fourth Edition.