I'm not really sure what to make of this, and invite comments. My best guess (and I emphasize the word guess) is that employers have made a concerted effort to combat sexual harassment through training and awareness, but they're focusing almost entirely on harassment of women. Note that the chart still shows that the vast majority of claims are filed by women, so this is not entirely irrational. However, the result is a decrease in sexual harassment of women with no impact on the claims filed by men.
What's your theory? Drop a comment or hit me on Twitter (@PhilipMiles).