Kanazawa mentions several times that his data on attractiveness are scored "objectively". The ratings of attractiveness made by the interviewers show extremely large differences in terms of how attractive they found the interviewee. For instance the ratings collected from Waves 1 and 2 are correlated at only r = .300 (a correlation ranges from -1.0 to +1.00), suggesting that a meager 9% of the differences in second wave ratings of the same individual can be predicted on the basis of ratings made a year before. The ratings taken at Waves 3 and 4 correlated between raters even lower, at only .136-- even though the interviewees had reached adulthood by then and so are not expected to change in physical development as strongly as the teenagers. Although these ratings were not taken at the same time, if ratings of attractiveness have less than 2% common variance, one is hard pressed to side with Kanazawa's assertion that attractiveness can be rated objectively.
The low convergence of ratings finding suggests that in this very large and representative dataset, beauty is mostly in the eye of the beholder.
So if I'm reading this right, the same cohort of young adults was 'measured' for attractiveness when they were 18-26, and then 6 years later when they were 24-32. If they had all been scored the same at both times, the correlation would be 1. If the scores were essentially random, the correlation would be 0. The correlation was in fact 0.136. Whatever these data are, they hardly seem to be an objective measure of anything that inheres in the research subjects.
Furthermore, in the data from the 24-32 year olds, which Kanazawa ignored for some reason, "there is no difference between the ethnicities in terms of ratings of physical attractiveness."