The main indicator of life satisfaction used by the OECD countries is average country score. The indicator is from the Gallup World Poll 2006 that is based on nationally representative samples of people aged 15 years and older. The Gallup World Poll asks respondents to "image an eleven-rung ladder where the bottom (0) represents the worst possible life for you and the top (10) represents the best possible life for you. On which step of the ladder do you personally stand at the present time?". The same questionnaire is used in countries.