http://finance.yahoo.com/q?s=VMMXX:

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Strange. The HTML source for this page shows a yield of 2.39%, not 92,318.20%. In both IE7 and Firefox, 2.39% shows up as the yield when the page is first rendered, but changes immediately to 92,318.20%. The yield is getting its significant digits from the Assets value, but why is a mystery to me.