After years in which many board members privately claimed that it was too difficult to find qualified women to serve as board members, 2018 is on pace to become a year in which a record number of women join boards.

The Wall Street Journal reports that women represented close to one third of new board members recruited to Russell 3000 boards during the first five months of this year, according to ISS Analytics. Specifically, 248 women joined boards so far this year while 553 men joined boards. In comparison, in all of 2017, 278 women joined boards while 775 men joined boards.

The increase hasn’t happened organically.

Powerful institutional investors including BlackRock, Calstrs and State Street have revised proxy voting guidelines to include provisions allowing for votes against nominating and governance committee chairs, members or the full board if diversity doesn’t improve. Investors have maintained that the focus on board diversity isn’t about social norms but about conclusive evidence that diverse groups make better decisions.