Although not all 20 million are men, I think we agree that all false accusations need to be prosecuted.

http://www.prosecutorintegrity.org/pr/survey-over-20-million-have-been-falsely-accused-of-abuse/

In 62% of cases, the false accusers were reported to be females. Often, the false allegation was made in the context of a child custody dispute — 27% of cases.

Similar percentages of falsely accused persons were seen among the various age groups, racial/ethnic categories, and geographical areas. In other demographic categories, however, substantial differences were unearthed.

The survey found a sharp gender divide – 11% of men, compared to 6% of women — reported being falsely accused.