Big name buyout firms have been unloading a record amount of shares in companies they have taken public, and show no sign of letting up.

Bain Capital, KKR, Apollo Global Management and other private-equity firms sold $20.5bn of stock through 50 so-called follow-on offerings during the first three months of 2013. That is twice as many deals as in the year-earlier period and the highest quarterly pace on record, according to Dealogic.