Hedge fund and private equity managers have been falling over themselves to sell stakes in their businesses, with at least 25 firms in the past year inviting outsiders in as minority or controlling owners.

They have taken at least $11bn (€8.25bn) in the past 12 months, with a further $4bn expected to come this month when buyout group Blackstone floats, according to research by Financial News and US corporate finance adviser Freeman & Co.