They have found that intellectually, the likeness tends to vanish regardless of the environment in which identical twins grow up. Inheritance amounts to more than half the characteristic personality traits. That is why eugenical improvement of the human race through parental selection has proved so difficult. Although it is seldom spoken about, nearly all societies protect themselves against population degeneration. In the United States , compulsory sterilization was legal in certain cases until 1973 .
European countries are less idealistic in that aspect.
Eugenics exists there and is practiced. All Nordic countries show similar figures. In Venezuela's case I don't have reliable figures because there are no official records about it. Your reader comments are always welcome.