Calculates absolute citizen congruence.
Vector for the representatives, or single point (e.g. government)
The representation score is calculated as: (1/N) * sum|Zi - median(R)|. There is a derivative (
accm) which uses the mean rather than the median here.
Golder, M., and J. Stramski. 2010. Ideological Congruence and Electoral Institutions. American Journal of Political Science 54 (1): 90-106.