ICI's latest "Money Market Fund Assets" report shows assets declining sharply during the week including the Sept. 15 quarterly tax date, after two weeks of modest declines. Their release says, "Total money market fund assets decreased by $39.69 billion to $4.46 trillion for the week ended Wednesday, September 15, the Investment Company Institute reported today. Among taxable money market funds, government funds decreased by $34.95 billion and prime funds decreased by $4.35 billion. Tax-exempt money market funds decreased by $395 million." Money fund assets are still up by $167 billion, or 3.9%, year-to-date in 2021. Inst MMFs are up $262 billion (9.5%), while Retail MMFs are down $95 billion (-6.2%). ICI's stats show Institutional MMFs decreasing $39.7 billion and Retail MMFs increasing $2.4 billion in the latest week. Total Government MMF assets, including Treasury funds, were $3.908 trillion (87.5% of all money funds), while Total Prime MMFs were $466.7 billion (10.5%). Tax Exempt MMFs totaled $90.4 billion (2.0%). Over the past 52 weeks, money fund assets have increased by $48 billion, or 1.1%, with Retail MMFs falling by $98 billion (-6.4%) and Inst MMFs rising by $146 billion (5.1%). (Note that ICI's asset totals don't include a number of funds tracked by the SEC and Crane Data, so they're almost $400 billion lower than Crane's asset series.) ICI explains, "Assets of retail money market funds increased by $2.37 billion to $1.43 trillion. Among retail funds, government money market fund assets increased by $3.49 billion to $1.14 trillion, prime money market fund assets decreased by $608 million to $216.53 billion, and tax-exempt fund assets decreased by $513 million to $78.99 billion." Retail assets account for just under a third of total assets, or 32.0%, and Government Retail assets make up 79.3% of all Retail MMFs. They add, "Assets of institutional money market funds decreased by $42.06 billion to $3.03 trillion. Among institutional funds, government money market fund assets decreased by $38.44 billion to $2.77 trillion, prime money market fund assets decreased by $3.74 billion to $250.12 billion, and tax-exempt fund assets increased by $118 million to $11.39 billion." Institutional assets accounted for 68.0% of all MMF assets, with Government Institutional assets making up 91.4% of all Institutional MMF totals.