Tax-exempt money market funds posted the second-largest outflows of the year — and more than doubled last week’s losses — as the total invested fell $5.42 billion to $363.09 billion in net assets for the week ending April 19, according to the Money Fund Report, a service of iMoneyNet.com.

Income-tax season and low yields driving investors to seek higher-yielding investments are to blame for this week’s significant outflows, according to Connie Bugbee, managing editor of report.

The funds lost $2.10 billion and closed with $368.51 billion for the week ending April 12, just ahead of the April 15 income tax deadline.

“This week traditionally is one in which assets flow out of the funds,” she wrote in the report. “In addition, the opportunity to invest directly in securities in an effort to attain slightly higher yield has been impacting money-fund asset flows since the beginning of 2010.”

Outflows had their highest level so far this year during the week ending Jan. 18, when tax-exempt money funds lost $7.66 billion and settled at $393.62 trillion in total net assets, according to iMoneyNet.com data.

But, Bugbee says, the outflow pattern this week is part of an annual trend. In 2009, tax-exempt funds saw outflows of $6.96 billion for the week ending April 20, on the heels of $2.88 billion for the week ending April 13 — just two days shy of the tax deadline.

Similarly, in 2008, the funds saw outflows of $7.26 billion for the week ending April 21, following losses of $2.85 billion for the week ending April 14.

This week, the average seven-day simple yield for the 495 tax-exempt funds in the report rose one basis point to 0.04% from the previous week, while the average maturity remained unchanged at 26 days.

The 1,169 taxable funds in the report had massive outflows of $52.72 billion this week as many investors liquidated assets to pay tax liabilities. Taxable funds settled at $2.486 trillion in total assets.

After 10 weeks in a row at 0.02%, the average seven-day simple yield for the taxable funds inched up one basis point to 0.03% this week.

Overall, the combined assets of the 1,664 money funds in the report decreased by $58.14 billion and closed with ­approximately $2.850 trillion in total

assets for the week ending April 20. The previous week had seen the funds lose $31.48 billion and end with assets of $2.908 trillion.

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