The usual approach is to look at economic indicators like GDP or employment figures, or social ones like literacy levels or crime rates.
But in Britain politicians are seeking a much more basic measure of the public's well-being: its happiness.
From this month, as part of an annual survey, 200,000 households in Britain will be asked some rather unusual questions. They are:
How happy are you? How happy did you feel yesterday? How anxious did you feel yesterday? To what extent do you feel the things in your life are worthwhile?
The large sample size means that researchers are hoping to minimise the questionnaire's margin of error. Statisticians will try to correlate respondents' answers about happiness to other variables, such as their income or where they live.
The Prime Minister David Cameron has signalled that he may allow his policies to be shaped by the responses to these questions.
But Sheila Lawlor, from the think tank Politeia, thinks that politicians should fix the economy before probing the national mood, which is less measurable.
"I don't think this [government] should start thinking about well-being and happiness, which are not very easy to measure; it should concentrate on a framework so we can have the things that will increase our well-being."