The measuring and monitoring children’s well—being is of growing importance to policymakers and those who strive to improve the lives of children everywhere. In the last decade, public attention has centered on children, a development driven by decreasing fertility in the most developed countries of the world and the postindustrial emphasis on human capital development. These developments position children at the center of the future capacity of a nation or region. Children have increasingly been identified as subjects with rights and entitlements of their own, as illustrated by the U. N. Convention on the Rights of the Child (CRC), which emphasizes a child’s right to develop his or her capacities. The CRC represents a milestone both in the understanding of children and in offering principles and guidelines for policies. The rights underscored by the convention require evidence on children’s well—being and theories or models for understanding their evolving capacities and development. The right to develop one’s capacities illustrates a complexity of analyzing children’s well—being: the analysis must encapsulate both the current standard of living and the potential for growth and future fulfillment arising from present conditions. Of course, systematic statistics on children have existed for a long time. However, new development in data and analytic resources and growing interest in childhood among social scientists have combined to advance child well—being to the forefront of research.