NEW YORK (AP) -- Total U.S. money market mutual fund assets fell $5.47 billion to $2.663 trillion for the week that ended Wednesday, according to the Investment Company Institute.

Assets in the nation's retail money market mutual funds increased $270 million to $917.72 billion, the Washington-based mutual fund trade group said Thursday. Assets of taxable money market funds in the retail category rose $2.37 billion to $726.63 billion. Tax-exempt retail fund assets fell $2.09 billion to $191.09 billion.

Assets in institutional money market funds fell $5.75 billion to $1.745 trillion. Among institutional funds, taxable money market fund assets fell $8.58 billion to $1.672 trillion. Assets of tax-exempt funds rose $2.83 billion to $72.91 billion.

The seven-day average yield on money market mutual funds was unchanged at 0.01% from the previous week, according to Money Fund Report, a service of iMoneyNet in Westborough, Mass. The 7-day compounded yield was flat at 0.01%.

The 30-day yield and the 30-day compounded yield were both unchanged at 0.01%, Money Fund Report said Wednesday.

The average maturity of portfolios held by money market mutual funds rose to 49 days from 47 days.

The online service said its survey of 100 leading commercial banks, savings and loan associations and savings banks in the nation's 10 largest markets showed the annual percentage yield available on money market accounts was unchanged at 0.12%.

The North Palm Beach, Fla.-based unit of Bankrate said Wednesday that the annual percentage yield available on interest-bearing checking accounts was unchanged from the week before at 0.05%. said the annual percentage yield on six-month certificates of deposit was unchanged at 0.14%, flat at 0.23% for one-year CDs and unchanged at 0.37% on two-year CDs. The five-year yield was unchanged at 0.79%.