The measure that compares the number of men to women in a population is
cohort
sex ratio
baby boomer
disengagement

   Sex ratio

Explanation:  The sex ratio or the gender ratio, as some argue, because according to some scientists these two terms are not interchangeable, is the ratio between the number of men and the number of women in the population. This ratio varies and depends on the type of society, i.e. it depends on economic, social, cultural, biological and technological conditions. The ratio of genders in the population, that is, the number of men and women can be affected by migration, higher mortality in some of the gender, as well as the average length of the life of the genders.

it's the under parts of the car