Flows into tax-exempt money market funds continued to see-saw as $906.5 million arrived in the week ended May 20 following outflows of $1 billion the previous week, according to The Money Fund Report, a service of iMoneyNet.com.

The industry has lost $6.21 billion since April 29, traditionally the end of heavy outflows associated with tax season. This year, the industry had about $17.21 billion of outflows during the four-week tax season that began April 1.

This week, the average, seven-day simple yield for the 423 tax-exempt reporting municipal funds was unchanged at 0.01%, while the average maturity fell one day to 27 days from the prior week.

The 1,026 reporting taxable money funds, meanwhile, gained $14.15 billion as total net assets settled with $2.324 trillion in the week ended May 21, compared to the previous week when inflows of $4.65 billion caused an increase in total net assets to $2.310 trillion.

The average, seven-day simple yield for the taxable money funds dipped by one basis point to 0.01% from the previous week, while the average maturity remained unchanged at 48 days.

Overall, the combined total net assets of the 1,449 money funds grew by $15.06 billion in the week ended May 21 to $2.583 trillion. That compares to the prior week when total net assets ended at $2.568 trillion after the arrival of $2.93 billion of inflows.