The median life of a private equity fund has risen to 15 years, according to Todd Miller, global co-head of secondary advisory at Jefferies Financial Group Inc.

“It blows apart the entire economics of PE funds,” said Hugh MacArthur, chairman of the global private equity practice at Bain & Co.

An analysis of value creation by vintage since 2005 across global private markets showed that returns, measured in multiples of investor contributions, start to stagnate after eight years before declining as holding periods extend, according to Kroll, which manages private equity disputes and fund restructurings.

Today, the industry has more than 32,000 unsold companies worth $3.8 trillion trapped in portfolios, according to Bain, while the payouts for investors, as a percent of the total net value of private equity’s portfolio, are at a near 16-year low.