Ahh, my favourite survey. The World Values Survey is academically-driven social survey originally developed to answer the question, "What makes people happy?". It investigates socio-cultural, moral, religious and political values of different cultures around the world and looks for the relationships between people's values and beliefs and their overall levels of well-being. First run in 1981, the survey is currently takes place around every 5 years, the most recent wave being 2005-6. The questionnaires from the most recent waves have consisted of about 250 questions. Now covering around 60 countries, the questionnaires are administered a worldwide total of about 92000 interviewees.

This example shows how level of happiness vary with a measure of a country's income per person.