Collective choice may tell nothing about anyone's individual preferences

As has been known for over a century, aggregated preferences of a group may bear little or no similarity to the preference of any single individual, regardless of the aggregation method. Yet, it remains routine to fit or test theories of individual decision making on pooled data, and it remains routine to cast theories of individual decision making at the aggregate level. This mindset may have disastrous policy and business implications. A population of individuals who all satisfy one theory may behave collectively as though they satisfied a competing theory. A collection of individuals satisfying a given theory may collectively satisfy a version of the same theory with qualitatively different scientific or decision analytic implications. Because the resulting artifacts apply at the population level, replications, large samples, and high-quality data can do nothing to detect or repair them.