The 13th straight month of withdrawals left the fund with $229 billion in assets as of the end of May, Chicago-based research company Morningstar Inc. said Monday in an e-mailed statement. That’s down from a peak of $293 billion last year.

Gross, 70, has struggled to reverse redemptions as the Pimco Total Return Fund trailed 71 percent of peers over the past 12 months. Gross said in an interview with Bloomberg Television last month that the Newport Beach, California-based firm will again rank at the top by the end of the year as wagers pay off.

Pimco in May outlined its new outlook for the next three to five years, saying that the economy is entering a “new neutral” era. This will be characterized by global growth converging toward lower, more stable speeds and interest rates that remain below their pre-crisis equilibrium, after five years of what Pimco called the “new normal” of below-average growth.

“The Pimco Total Return Fund delivered strong performance in May ahead of 79 percent of peer funds as the bond market sided with Pimco’s new neutral view that policy rates will stay lower for longer,” Mark Porterfield, a spokesman for the firm, said in an e-mailed statement. “We continue to see opportunity in bonds as a portfolio diversifier and as a way to generate the kind of long-term outperformance that our clients have come to expect from Total Return and all of Pimco’s strategies.”

Former Status

Pimco Total Return Fund is a formerly top-ranked fund whose five-year ranking has slipped to the 56th percentile, according to data compiled by Bloomberg. The fund has climbed 3.3 percent this year, the data show, helped by a 1.25 percent gain last month.

Gross’s fund lost a record $41.1 billion to withdrawals in 2013 and $15.6 billion so far this year, according to Morningstar.

Morningstar estimates deposits or withdrawals for mutual funds by computing the change in assets on a monthly basis that isn’t accounted for by performance. The fund’s actual withdrawals or deposits may differ from Morningstar’s estimates because of the timing of purchases and redemptions or dividend distributions.