Assets invested in money market mutual funds reached $601.76 billion in the week ended Dec. 8, the Investment Company Institute reported.

That is a strong increase from $588.68 billion the prior week. It marks the first time since October 1992 that money market fund assets have topped the $600 billion level, according to the institute.

Assets rose in all four categories tracked by the Washington-based trade group: taxable and tax-exempt funds for retail customers and institutional investors.

Retail funds closed the week with $400.53 billion of assets, a $3.72 billion gain. Taxable money market funds held $311.67 billion of the total, while tax-exempt funds held $88.86 billion.

Institutional funds had $201.23 billion of assets, up $9.36 billion in the week. Taxable money market funds accounted for $178.16 billion, with tax-exempt funds making up the balance of $23.06 billion.

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