the index uses 24 variables (which include both hard data and survey data) across 11 sectors to create a measure of welfare for 34 of its member countries, plus Brazil and Russia.
GAO Report GAO-05-1. GAO studied a diverse set of key indicator systems that provide economic, environmental, social and cultural information for local, state, or regional jurisdictions covering about 25 percent of the U.S. population—as well as several systems outside of the United States. GAO found opportunities to improve how our nation understands and assesses its position and progress.
B. Shapira, M. Taieb-Maimon, and A. Moskowitz. Proceedings of the 2006 ACM symposium on Applied computing, page 1118--1119. New York, NY, USA, ACM, (2006)