Methodology on the expanded historical series from 2004 to 2010 has not been updated (mba.org)
Mathematical Geology 37:127 - 140) I showed that the effect of dating error in proxy records is to reduce the amplitude of peaks in historical series. (blogs.nature.com)
In Table 6 (1960) and Table 7 (1965), Easterlin (1974) presented the rating of personal happiness (min: 0; max: 10) of fourteen countries and the percentage distribution of population by happiness of nine countries, respectively, and asked on page 108: «What one would like most, of course, is historical series on happiness as countries developed?» (scirp.org)