mox, my information is from a report issued by the US census bureau, issued in 2003, which is based on data from 2002. I did combine age groups in my previous post, but that decrease in the ratio of men to women does indeed exist in the data.
In more detail, the report states that there are 104.1 boys for every 100 girls under 5, and 105 boys for every 100 girls in the 5 to 17 range. For the 18-24 range, there are 100.1 men for every 100 women, and in the 25-29 age range there are 99.9 men for every 100 women. According to the footnotes, the data excludes members of the armed forces who do not have a civilian adult in the household, and counts only non-institutionalized citizens. Of course, men are more likely to serve in the armed forces and to be incarcerated than are women. I’d also guess that men in the 18-29 age group are more likely than women to die from most causes, including accidents, murder, and suicide. (It would be interesting to see this breakdown with narrower age bands)Both these factors, which help account for the sharp decrease in the ratio of men to women in the 18 to 29 age range, would probably affect frum Jews to a lesser extent than the general population.