Angus Maddison's *Monitoring the World Economy, 1820-1992* is a comprehensive study of global economic trends from the Industrial Revolution to 1992. The book, published by the OECD, provides consistent estimates of GDP, population, and GDP per capita for 56 countries, covering over 90% of world product. It also includes less complete series on employment, exports, capital stocks, and productivity measures. Maddison relies on a wide range of sources, corrects for discontinuities, and adjusts data for comparability and continuity. The appendices contain the core data, accompanied by a general analysis of long-run economic growth and development within a growing world economy framework. Maddison's prestige and the OECD's endorsement make this dataset highly valuable, potentially increasing scholarly productivity in teaching and research. However, the book's title is misleading, as there is limited useful content before 1870, especially for the non-Western world. Maddison's early per capita income estimates are often tentative, and his historical income estimates for poor countries are less consistent with general trends. While Maddison has adapted and maintained intellectual integrity, users should be cautious and recognize the need for further scrutiny, particularly for historical income estimates for less developed countries (LDCs). For developed countries, especially after 1900, Maddison's estimates are more reliable.Angus Maddison's *Monitoring the World Economy, 1820-1992* is a comprehensive study of global economic trends from the Industrial Revolution to 1992. The book, published by the OECD, provides consistent estimates of GDP, population, and GDP per capita for 56 countries, covering over 90% of world product. It also includes less complete series on employment, exports, capital stocks, and productivity measures. Maddison relies on a wide range of sources, corrects for discontinuities, and adjusts data for comparability and continuity. The appendices contain the core data, accompanied by a general analysis of long-run economic growth and development within a growing world economy framework. Maddison's prestige and the OECD's endorsement make this dataset highly valuable, potentially increasing scholarly productivity in teaching and research. However, the book's title is misleading, as there is limited useful content before 1870, especially for the non-Western world. Maddison's early per capita income estimates are often tentative, and his historical income estimates for poor countries are less consistent with general trends. While Maddison has adapted and maintained intellectual integrity, users should be cautious and recognize the need for further scrutiny, particularly for historical income estimates for less developed countries (LDCs). For developed countries, especially after 1900, Maddison's estimates are more reliable.