I'm thinking the change from equal numbers of men and women changed because of World War II in the U.S.

Because they said this ratio of 98 men for every 100 women has remained somewhat constant since 1946 here in the U.S. which is interesting in itself whereas the 20 million people (mostly men but also women and children that died in Russia during World war II) really unbalanced Russian Ratio of women to men which is still around only 85 men for every 100 women there today.