Affected people are just the tip of a genetic iceberg. Most people do not know that they are carriers unless they have a child with the disease. Sterilizing affected people will not prevent those who are silent carriers from having affected children. The ratio of carriers to people with a disorder increases as the percent of carriers in the population decreases. Using a mathematical formula called the Hardy-Weinberg Law, it is possible to calculate exactly what effect a perfectly efficient sterilization program for all affected individuals would have on the frequency of a gene in a population.
Most recessive genes are rare.
Suppose that 1 in 100 people carries the gene. Clearly a negative eugenics plan of sterilization affected people would have no noticeable effect on the numbers of persons born with the disorder. In theory, sterilizing all carriers would work to reduce the incidence of genetic disorders. The problem is that it would drastically reduce the number of people who would be allowed to reproduce. And that s just one disorder.