Prisoner sex ratios across jurisdictions have a distribution that is relatively easy to understand and communicate. Prisoner sex shares, in contrast, have an obscure distribution. Prisoner sex ratios are approximately log normally distributed. Hence small percentage differences in prisoner sex ratios are approximately intervals in the log normal probability distribution. A statement such as “10% higher than the median sex ratio” maps easily to a position on a well-known normal curve. Statements such as “10% higher than the median sex share” are confusing, because sex shares themselves are themselves expressed as percentages, e.g. 95% of prisoners are men. Moreover, statements in sex shares have much less intuitive statistical meaning because the shape of the sex-share distribution is asymmetric and not well-known. Moreover, the distribution of prisoner sex shares is bounded above by 100%. Hence having a 50% greater sex share is impossible if the sex share is greater than two-thirds. Having a 50% greater sex ratio than the median prisoner sex ratio is possible and frequently occurs.

Sex disparity in college graduation rates also illustrates that sex ratios are more insightful than sex shares. Women earned 59% of the associates or bachelor degrees that U.S. colleges and universities awarded in the academic year 2009-2010. That’s equivalent to 1.42 women per man receiving a college degree. Compared to the sex share of college degrees, the sex ratio better communicates the significance of the college-graduate sex disparity for heterosexual dating and mating.