Both across states within the U.S. and internationally, the dispersion of the prisoner sex ratio has decreased over time. Reasonably good, state-level prisoner statistics for the U.S. exist from 1880. The sex-ratio dispersion index across U.S. states in 1880 was 1.43. It dropped to about 0.6 on either side of World War II, and then to 0.4 in 2000-2010. For 45 international jurisdictions for which prisoner data are available for 1977 and 2010, the sex-ratio dispersion index fell from 0.72 to 0.63. Networks of communication and knowledge regulate variation by establishing what is normal and what is unusual. Increased communication across jurisdictions may have lessened variation in the prisoner sex ratio over time.
The dispersion of the prisoner sex ratio distribution internationally is similar to the dispersion of the prisoner sex ratio distribution in the U.S. roughly a century ago. In 2010, across 209 international jurisdictions covering 98% of the world’s population, the sex-ratio dispersion index was 0.90. That’s about the same level of dispersion that existed across U.S. states in 1910. At least superficially, world jurisdictions in 2010 had more varied political cultural and legal systems than did U.S. states in 1910. On the other hand, globalization and transnational institutions of professional expertise may constrain the sex composition of prisoners more than similar effects did within the U.S. in 1910.
The strength of professional norms in the administration of criminal justice may be more significant for prisoner sex-ratio dispersion than apparent differences in political culture and legal systems. For example, jails and prisons now are normally constructed with separate facilities for male and female prisoners. Criminal justice systems, like other bureaucracies, tend to utilize available resources. Standardized prison plans thus affect prisoner sex ratios indirectly through physical structures. Similar effects may occur through model laws, uniform crime reporting, and less tangible norms of criminal culpability.