Tax-exempt money market funds struggled to hang onto the previous week’s gains as $1.72 billion exited the industry and total net assets settled at $258.36 billion in the week ended May 13, according to The Money Fund Report, a service of iMoneyNet.com.

This week’s decrease offset some of the $667.90 million that trickled back into tax-exempt money funds last week following $4.49 billion of outflows in the week ended April 29 at the tail end of income tax season -- a period typically characterized by heavy declines in assets.

The average, seven-day simple yield for the 423 reporting tax-free money funds remained unchanged at 0.01% for the second week in a row, while the average maturity remained at 28 days.

In the taxable money market, the total net assets of the 1,029 reporting money funds rose by $4.65 billion to $2.310 trillion in the week ended May 14, which compares to the prior week when the funds had inflows of $5.97 billion and total net assets rose to $2.305 trillion.

The average, seven-day simple yield for the taxable money funds remained at 0.02% from the prior week, while the average maturity remained at 48 days.

Overall, the combined assets of the 1,452 reporting money funds increased by $2.93 billion during the week ended May 14 as total net assets rose to $2.568 trillion. That compares to the arrival last week of $6.63 billion of inflows as total net assets increased to $2.565 trillion.