Measurement issues such as the reliability and validity of the replies, whether
respondents report their true feelings, and possible biases resulting from the
context in which the question is asked, have been extensively studied in the
literature (see Diener (1984) and Veenhoven (1993)). The general conclusion
of such assessments is that subjective indicators such as those used here,
though not perfect, do re¯ect respondents' substantive feelings of well-being ±
in the words of psychologist Ed Diener (1984, p. 551), the `measures seem to
contain substantial amounts of valid variance.'