Women are conditioned from the very earliest ages via viscous stigmas, that keeping her sexual partners a secret and never admitting to more than a few is always the way to go.
Men historically cheated more but in todays more liberal age were those stigmas are being torn away from women they are passing men, in general for both cheating and casual partners.
And men generally have no chance in this race. Women will just rack up way more numbers as they continue to be unleashed.