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Bill Gross, manager of the Janus Henderson Global Unconstrained Bond Fund, best known for his time managing the Pacific Investment Management Co.’s Total Return Fund, has decided to retire.

Gross has spent over forty years changing the way people invest in bonds. Bloomberg reports:

Gross, who announced his retirement Monday, struggled in the last four years as head of the Janus Henderson Global Unconstrained Bond Fund. His performance failed to match the stellar track record he achieved while building Pacific Investment Management Co.’s Total Return Fund into a bond giant.

“I look back on it and the performance of the unconstrained fund in the past four years with Janus has been unsatisfactory, no doubt,” Gross said in an interview with Tom Keene on Bloomberg TV. “Maybe I should have stuck to total return and been more constrained.”

Gross joined Janus Henderson Group Plc in late 2014. At Janus, Gross has seen assets in his unconstrained fund plummet and annualized returns of less than 1 percent. Responsibilities for the fund will be assumed by the team that has been supporting Gross, Janus said.

In his next phase, Gross, 74, will focus on managing his personal assets and remain active in charitable endeavors, according to a statement from Janus. He has made philanthropic donations of $800 million in the past 20 years.

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