Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

Why is the price of my investment only updated once per day?
There is no fundamental, good reason, I think; "that's just how it's done" (which is what all the other answers seem to be saying, w/o coming out and admitting it). Just guessing, but I'll bet most of the reason is historical: Before up-to-the-moment quotes were readily available, that was a bit tedious to calculate/update the fund's value, so enacted-laws let it be done just once per day.  (@NL7 quotes the security act of 1940, which certainly has been updated, but also still might contain the results of crufty rationales, like this.) There are genuinely different issues between funds and stocks, though: One share of a fund is fundamentally different from one share of stock: There is a finite supply of Company-X-stock, and people are trading that piece of ownership around, and barter to find an mutually-agreeable-price.  But when you buy into a mutual-fund, the mutual-fund "suddenly has more shares" -- it takes your money and uses it to buy shares of the underlying stocks (in a ratio equal to its current holdings).  As a consequence: the mutual fund's price isn't determined by two people bartering and agreeing on a price (like stock); there is exactly one sane way to price a mutual fund, and that's the weighted total of its underlying stock.  If you wanted to sell your ownership-of-Mutual-Fund-Z to a friend at 2:34pm, there wouldn't be any bartering, you'd just calculate the value based on the stated-value of the underlying stock at that exact moment. So: there's no inherent reason you can't instantaneously price a mutual fund.  BUT people don't really buy/sell funds to each other -- they go to the fund-manager and essentially make a deposit-or-withdraw.  The fund-manager is only required by law to do it once a day (and perhaps even forbidden from doing it more often?), so that's all they do. [Disclaimer: I know very little about markets and finance. But I recognize answers that are 'just because'.]