(Bloomberg) -- Pacific Investment Management’s biggest mutual fund had the worst year of client withdrawals in the history of fund management as the firm lost both of its co-chief investment officers, Bill Gross and Mohamed El-Erian.

Investors pulled $19.4 billion from Pimco Total Return Fund in December, bringing redemptions in 2014 to a record $105 billion, according to data compiled by Bloomberg using information from Newport Beach, California-based Pimco and Morningstar Inc. Assets in the world’s biggest bond fund fell to $143.4 billion as of Dec. 31, according to a Jan. 2 statement from Pimco, down by more than half from a peak of $293 billion in April 2013.

“No doubt, it is the largest outflow for one year in dollar terms,” among money managers, according to Russel Kinnel, director of mutual-fund research at Chicago-based research firm Morningstar.

Pimco is seeking to reassure investors and stem redemptions after Gross left on Sept. 26, bringing back high-profile money managers and naming top performers to run its largest funds. The Total Return Fund, which was once the biggest U.S. mutual fund, is now the fourth-largest as offerings from Vanguard Group have overtaken it, according to data compiled by Bloomberg. The decline has erased more than five years of growth at the fund, bringing assets to 2008 levels.

“The pace of outflows during December continued to be significantly below the peak in September and early October 2014,” spokesman Daniel Tarman said in an e-mailed statement on Jan. 2. “The fund’s experienced portfolio management team remains focused on pursuing investment opportunities designed to play out over the medium and long-term, while retaining a focus on capital preservation and liquidity for shareholders.”

WEATHERING WITHDRAWALS

Pimco can weather withdrawals from institutional and retail clients of as much as $350 billion without hurting performance, according to Morningstar. Pimco had $1.87 trillion in assets under management as of Sept. 30.

Last month’s redemptions from the fund followed a combined $60.5 billion in September, October and November, including a record $27.5 billion in October. In 2013, clients pulled $41.1 billion from the fund, according to Morningstar estimates.

Pimco Total Return, managed by Chief Investment Officers Scott Mather, Mark Kiesel, and Mihir Worah since Gross’s departure, trailed a majority of peers for the second straight year in 2014 after missing a rally in longer-term bonds and betting that inflation would rise. The fund returned 4.7% in 2014, trailing 53% of comparable funds, after losing 1.9% the previous year, behind 65% of peers, according to data compiled by Bloomberg.

“You could still see some more outflows and then it probably stabilizes, unless performance really deteriorates,” Michael Rosen, chief investment officer at Angeles Investment Advisers in Santa Monica, California, said in a telephone interview.

GROSS, EL-ERIAN

The fund had more than doubled from $132 billion at the end of 2008, after navigating the financial crisis with returns that beat 82% of rivals. Assets peaked in April 2013, before the Federal Reserve hinted it would unwind stimulus measures, sparking redemptions and unsteady performance.

Gross, who co-founded Pimco in 1971 and built it into one of the nation’s largest money managers, left after deputies including now-group Chief Investment Officer Daniel Ivascyn said they would quit and management debated his ouster, according to people familiar with the matter. Gross resigned to run an unconstrained fund at Denver-based money manager Janus Capital Group Inc.

El-Erian, who shared the role of CIO with Gross and served as Pimco’s chief executive officer, in January announced his resignation from the firm. El-Erian is now chief economic adviser at Pimco’s parent Allianz SE and a contributor to Bloomberg View.

Bond firms including DoubleLine Capital have benefited as investors are reviewing their investments with Pimco. DoubleLine, the bond firm co-founded by Jeffrey Gundlach, received $2.2 billion in December, bringing last year’s total of net new money to $10.9 billion, the Los Angeles-based firm said in a statement.

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