Vanguard Sent Wrong Data to Investors

He attributed the error to a computer glitch, which is nothing new for Vanguard nor for many other asset managers. In Monday's frenetic rally on Wall Street, customers of Vanguard, Fidelity, Merrill Lynch, Charles Schwab and TD Ameritrade reported issues logging into their accounts.

(Related: Trading Outages at Schwab, E-Trade, TD Ameritrade, Other Platforms Irk Investors)

Vanguard's computer problems are "a sign of too much growth too fast without having the systems in place to keep up with it," Weiner said. "They're in the big leagues now and need to have systems that reflect that."

Morningstar strategist Alec Lucas cautioned that investors should not overreact to Vanguard's money market reporting problem because the mistake did not affect what investors earned but rather what they were projected to earn in an asset class that is not expected to generate big returns.

But he noted that there have been questions on whether Vanguard has invested enough in technology and customer services because of its "lean cost structure," which also benefits investors indirectly: Under its ownership structure, Vanguard fund investors own Vanguard funds and therefore Vanguard.

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