Economics is everywhere, so the 21st edition continues our commitment to providing instructors with accessible and intuitive coverage of a wide variety of economic subject areas. To that end, we are happy to report that we have been able to pull material that appeared only online in previous editions into the printed book. That includes what were previously two full-length Web Chapters as well as a large fraction of the material that had been posted online as Content Options for Instructors (COIs). “Technology, R&D, and Efficiency,” which had previously been a Web Chapter, is now Chapter 15, while “The Economics of Developing Countries,” also previously a Web Chapter, is now Chapter 42. Those chapters as well as the material on “Previous Exchange Rate Systems” that had been posted online as Content Options for Instructors 2 (COI2) are now integrated directly into the printed book, the latter becoming an appendix to Chapter 41 (The Balance of Payments, Exchange Rates, and Trade Deficits). The only online material that was not brought into the book was COI1, “The United States in the Global Economy.” That content largely duplicated material that appeared in other chapters and was not much used, so it will no longer be supported either online or in print.

经济学无处不在，因此第21版继续我们的承诺，为教师提供各种各样的经济学科领域的方便和直观的报道。为此，我们很高兴地报告说，我们已经能够将以前版本中只在网上出现的材料放入印刷本中。这包括了之前两个完整的网络章节，以及一大部分被发布到网上的内容选项，为教师（coi）。“技术、研发和效率”以前是网络章节，现在是第15章，而“发展中国家的经济”以前也是网络章节，现在是第42章。这些章节以及“以前的汇率制度”的材料已经在网上发布，作为讲师2（COI2）的内容选项，现在被直接整合到印刷本中，后者成为第41章（国际收支、汇率和贸易逆差）的附录。唯一没有被纳入这本书的在线材料是COI1，“全球经济中的美国”。这一内容基本上重复了其他章节中出现的材料，而且使用不多，因此它将不再支持在线或印刷。