Percent replying "The environment" to 1a: "Which of these issues is the most important for [COUNTRY] today?" plus percent replying "The environment" to 1b: "Which of these issues is the next most important for [COUNTRY] today?". The issues in the list include: (1) Health care, (2) Education, (3) Crime, (4) The environment, (5) Immigration, (6) The economy, (7) Terrorism, (8) Poverty, (9) None of these, (98) Can't choose.

In Environment III (2010) - questions 1a and 1b.
In Environment II (2000) - question not part of the survey.
In Environment I (1993) - question not part of the survey.

The higher the score the higher the percentage of the population that prioritizes the environment as the most or second most important issue. The lower the score the smaller the percentage of the population that prioritizes the environment as the most or second most important issue.