The volume of US debt affected by fallen angels, companies that have dropped from investment grade, has tripled from the same time last year due to private equity buyouts.

So far this year there have been eight fallen angels affecting rated debt worth $29.5bn (€22.1bn) according to ratings agency Standard & Poor's. In the same period last year, 10 issuers were downgraded to speculative grade affecting $12.6bn in rated debt.