This chapter looks at the uses of survey methodology in the description and explanation of the greening of public opinion aimed at the production of knowledge relevant for decision making on environmental issues, with illustrations provided by research conducted in developing societies such as Brazil and Mexico. Dunlap et al. sound just overjoyed by findings that they believe allow them to challenge conventional wisdom as well as theoretical knowledge—notably Ronald Inglehart's work on the linkages between post-materialist values and socio-economic development. The other dimension of behavior, green activism is measured by the Health of the Planet Survey (HPS) by looking at participation in a group or organization that works to protect the environment. The proportion of Mexican activists is twice as large as the one of Brazilians. In the HPS, Brazil appears as the country with the smallest percentage of green consumers only matched by India whereas Mexico stands closer to East Asian and Eastern Europe.