Studies have shown that men have accumulated more assets in their employer, sponsored 401(k) plans then women. There are a number of reasons why this has occurred in the past, although, the gap, among younger folks in the workforce, appears to be tightening, as between men and women. Marriages also are a factor along with the birth of children, which requires the mothers to stay home, and many cases, for an extended period…. It is my fervent hope that this gap will continue to close as time passes…. 
https://www.fa-mag.com/news/men-s-401-k–balances-average-50–higher-than-women-s–bofa-finds-73724.html