Part 1: Comparing responses to different survey questions on the same topic -- Problems and conventional solutions -- chap. 1 Diversity in survey items and the comparability problem -- Part 2: Innovation 1: The happiness scale interval study -- chap. 2 The happiness scale interval study -- chap. 3 Use of happiness scale interval studies in this book -- chap. 4 Equivalence of rating scales using different keywords -- chap. 5 ‘Very Happy’ is not always equally happy -- chap. 6 A change in response scale comes with another interpretation of the labels: the japanese case (pm) -- Part 3: Innovation 2: The continuum approach -- chap. 7 The continuum approach -- Part 4 Innovation 3: The reference distribution method -- chap. 8 The reference distribution method -- chap. 9 Stability of the boundaries between response options for different countries -- chap. 10 Analyses of differences in trends among the happy few and the unhappy few -- chap. 11 Combining and pooling time series on life satisfaction in Japan and The Netherlands -- chap. 12 Directions for further research -- Appendices.