An article in today's Wall Street Journal (2015-08-16) titled A New Computer Glitch is Rocking the Mutual Fund Industry is all about how some kind of computer (software?) failure at a company called SunGard Data Systems Inc. is impacting large mutual fund and ETF companies in that they're unable to accurately value their funds (compute the net asset value).

Several traders said they were forced to calculate their own net asset value for ETFs and that they widened the spreads, or the difference, between listed buying and selling prices to accommodate for the higher risk of trading.

So, putting aside ETFs for the moment (perhaps they need valuations during the day) a mutual fund's valuation is published once per day, at close of market.

Given that a mutual fund manager knows, at the end of the day, precisely how many shares/units/whatever of each investment (stock, equity, etc.) they own, plus their bank balance, what is there about exactly computing a mutual fund's value that can't be done with a query against finance.yahoo.com and a very simple Excel spreadsheet?

2 Answers 2


Given that a mutual fund manager knows, at the end of the day, precisely how many shares/units/whatever of each investment (stock, equity, etc.) they own, plus their bank balance,

It is calculating this given. There are multiple orders that a fund manager requests for execution, some get settled [i.e. get converted into trade], the shares itself don't get into account immediately, but next day or 2 days later depending on the exchange. Similarly he would have sold quite a few shares and that would still show shares in his account.

The bank balance itself will not show the funds to pay as the fund manager has purchased something ... or the funds received as the fund manager has sold something.

So in general they roughly know the value ... but they don't exactly know the value and would have to factor the above variables. That's not a simple task when you are talking about multiple trades across multiple shares.


Remember that in most news outlets journalists do not get to pick the titles of their articles. That's up to the editor. So even though the article was primarily about ETFs, the reporter made the mistake of including some tangential references to mutual funds. The editor then saw that the article talked about ETFs and mutual funds and -- knowing even less about the subject matter than the reporter, but recognizing that more readers' eyeballs would be attracted to a headline about mutual funds than to a headline about ETFs -- went with the "shocking" headline about the former.

In any case, as you already pointed out, ETFs need to know their value throughout the day, as do the investors in that ETF. Even momentary outages of price sources can be disastrous.

Although mutual funds do not generally make transactions throughout the day, and fund investors are not typically interested in the fund's NAV more than once per day, the fund managers don't just sit around all day doing nothing and then press a couple buttons before the market closes. They do watch their NAV very closely during the day and think very carefully about which buttons to press at the end of the day. If their source of stock price data goes offline, then they're impacted almost as severely as -- if less visibly than -- an ETF.

Asking Yahoo for prices seems straightforward, but (1) you get what you pay for, and (2) these fund companies are built on massive automated infrastructures that expect to receive their data from a certain source in a certain way at a certain time. (And they pay a lot of money in order to be able to expect that.) It would be quite difficult to just feed in manual data, although in the end I suspect some of these companies did just that. Either they fell back to a secondary data supplier, or they manually constructed datasets for their programs to consume.

  • Thanks. BTW, referring to yahoo and Excel was an exaggeration for effect... But I think your answer doesn't really get to the heart of the question, which is: cash + sum over (# shares * most recent price) = NAV, yes or no? Apparently no, so what else is there? Exactly what is going on that you outsource to a third party this calculation which you could easily do yourself?
    – davidbak
    Aug 28, 2015 at 17:01
  • Yes, the calculation is simple. No, a company can't generate stock prices themselves. They need to subscribe to the market feeds or use a vendor who subscribes to the market feeds (see the link in my answer). In this case it sounds like one of the popular vendors broke down, so their customers couldn't get the prices.
    – dg99
    Aug 28, 2015 at 19:25

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