Characteristics of the study population (n = 13 931) compared to the adult general population in Sweden, retrieved from Statistics Sweden.

OECD = Organisation for Economic Co-operation and Development; EUR = Euro. aFor statistical significance between respondents and non-respondents using t-test for comparing mean ages and χ2 test for comparing categorical variables. bSeptember 24th 2010, just before the survey was sent. cSignificant difference between the respondents and non-respondents. dNon-significant difference between the respondents and non-respondents. eIn 2010. fIn 2009 before taxation. Yearly average exchange rate in 2009 from Swedish krona to Euro 10.6213.