Money market mutual funds picked up more than $3 billion in assets during the week that ended Jan. 4, reversing four straight weeks of outflows, according to the Investment Company Institute.

Assets rose to $631.69 billion, up 0.6% from $628.22 billion on Dec. 28.

The week's gains were most pronounced on the retail side. Individual investors added $2.82 billion to money funds, bringing total assets to $446.15 billion. Taxable funds held $352.74 billion, up $1.22 billion in the week, while tax-exempt funds held $93.41 billion, a $1.59 billion rise.

Institutional investors added $1.31 billion to money funds, boosting this category to $185.54 billion. That includes $161.08 billion in taxable money funds, up $332.6 million, and $24.47 billion in tax-exempt funds, a $979.4 million increase.

Money market mutual funds have been posting strong asset gains since last summer, when balances hovered below $600 billion. The surge in money fund assets "coincides with the well-documented outflows from bond funds and the rise in short-term rates," said a spokesman for the Washington- based institute.

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