This book is about development and measuring development progress. While precise definitions may vary, development is, at heart, a process of building wealth, the produced, natural, human, and institutional capital which is the source of income and wellbeing. A key finding is that it is intangible wealth, human and institutional capital, which dominates the wealth of all countries, rising as a share of the total as countries climb the development ladder. The book is divided into two parts. The first part provides the big picture of changes in wealth by income group and geographic region, with a focus on natural capital because it is especially important for low-income developing countries. The second part presents case studies that illustrate particular aspects of wealth accounting, including accounting for climate change, the role of intangible capital in growth and development, measuring human capital, and the use of wealth accounting to improve transparency and governance in resource-rich economies. The final chapter reports on the implementation of wealth accounting by countries. The appendixes provide the full wealth accounts for individual countries and for aggregations by income group and geographic region.