Sex Ratios – Primary and Secondary
I wanted to put together a table that showed the various ways that sex ratios can be expressed. This was prompted by the large number of writers who present sex ratios in a non-standard and misleading way. This post is on the dry side since it is about numbers, but I hope readers will gain and understanding of how various numbers can represent the same quantity.
The terms I’ll use for the ratios and proportions are: Sex Ratio, Gender Feminist, and Proportion. I find that sex ratios can be presented in any of these varieties and wanted a simple way to compare numbers to see which were equivalent.
Sex Ratio is the number of males per one-hundred females. This is the standard format for a sex ratio. Variations do occur so 106, 1.06, and 1060 are equivalent.
The Gender Feminist number is the number of females per 1000 males. This method is often used to claim that girls are being preferentially aborted. The number of girls born per 1000 boys will always be less than 1000 for a normal range of sex ratios.
Proportion is the number of males divided by the total of males and females multiplied by 100. The result is straightforward, and the percent girls can easily be determined.
When evaluating information, one must take care to note whether the sex ratio or proportion is used. And to note whether the standard sex ratio of boys per girls or the gender feminist variance is used.
The primary sex ratios table is given first and the secondary ratios table. I have also given examples in the secondary sex ratio table to indicate where various countries fall. I have also included some numbers associated with environmental and employment events.
| Sex Ratio | Gender Feminist | Proportion |
| 125 | 800 | 55.56% |
| 130 | 769 | 56.52% |
| 140 | 714 | 58.33% |
| 150 | 667 | 60.00% |
| 160 | 625 | 61.54% |
| 170 | 588 | 62.96% |
| 180 | 556 | 64.29% |
The primary sex ratio is not easy to determine with precision. This number refers to the number of boys per one-hundred girls at conception. Physically we are all alike at this point so even if the newly fertilized egg could be examined, we still would not know whether it were a boy or girl.
Extrapolation based on the sex of fetuses that die before birth is a way of working out the ratio. For abortion, that number is unknown; at least in the State of Wisconsin where no recording of the sex of the aborted fetus is required.
Ultrasound numbers may help, but are not always reliable. At twelve weeks gestation, according to some studies, the accuracy is 80%. The result is also dependent on the person who reads the ultrasound and the cooperation of the fetus.
At any rate, the number of boys conceived to the number of girls can be quite high; up to 170. If factors are such that viability of boy fetuses is increased then the secondary sex ratio (birth ratio) can easily range to 115 or perhaps even 120 and still be normal.
| Sex Ratio | Gender Feminist | Proportion | Examples |
| 54 | 1852 | 35.06% | Fathers employed in aluminum plants (1) |
| 62 | 1613 | 38.27% | Dioxin spill(2) |
| 66 | 1515 | 39.76% | Fathers employed in pesticide plants(3) |
| … | … | … | … |
| 102 | 980 | 50.50% | South Africa |
| 103 | 971 | 50.74% | |
| 104 | 962 | 50.98% | Iceland |
| 105 | 952 | 51.22% | India, United States |
| 106 | 943 | 51.46% | World |
| 107 | 935 | 51.69% | Spain |
| 108 | 926 | 51.92% | |
| 109 | 917 | 52.15% | |
| 110 | 909 | 52.38% | Albania |
| 111 | 901 | 52.61% | |
| 112 | 893 | 52.83% | China |
| 113 | 885 | 53.05% | |
| 114 | 877 | 53.27% | |
| 115 | 870 | 53.49% | |
| 116 | 862 | 53.70% | Georgia |
| 117 | 855 | 53.92% | Armenia |
The secondary sex ratio is the number that gives the number of boy births per 100 girl births. The example country data are from the 2006 CIA World Fact Book. Most countries can be very accurate about the birth ratios. Sex of the child is noted on a birth certificate and duly recorded. Countries with a dysfunctional infrastructure can be problematical.
What is a normal secondary sex ratio? There isn’t one. When extreme proportions like sixty percent boys or girls occur, we can be sure of abnormality and attempt identify a cause. For smaller variations around the world average, it is difficult to distinguish natural variations from other factors. If the ratio drops below 100 that would be abnormal.
More important, abnormal events such as a low ratio of boys, are also associated with increased birth defects, and the workplace environment of the father. The hazard is sufficient that men need to be warned about the consequences of their employment on their offspring.
(1) Davis, D. L., Gottlieb, M. B., & Stampnitzky J. R. (1998). Reduced ratio of births in several industrialized countries. Journal of the American Medical Association, 279(13), 1018-1023.
(2) Mocarelli, P. (2000). Paternal concentrations of dioxin and sex ratio of offspring. Lancet, 355, 1858-1863.
(3) Ryan, J. J., Amirova, Z., & Carrier G. (2002). Sex ratios of children of Russian pesticide producers exposed to dioxin. Environmental Health Perspectives, 110(11).
in category Seeking Perspective
