My online broker, Fidelity, says that I have 0.16 shares of MSFT. How is this possible? I always assumed that you had to own a whole number of shares.
It's not that uncommon but it doesn't usually come from standard purchases. Investopedia explains:
Definition of 'Fractional Share'
A share of equity that is less than one full share. Fractional shares usually come about from stock splits, dividend reinvestment plans (DRIPs) and similar corporate actions. Normally, fractional shares cannot be acquired from the market.
However, there is at least one investment firm that markets itself as offering fractional shares. Fractional investing makes more sense, since an investor's perspective is to invest a certain number of dollars into equity, not to buy a certain number of shares that closely mirror the dollar commitment.
Theoretically, yes, you can only buy or sell whole shares (which is why you still have .16 shares in your account; you can't sell that fraction on the open market). This is especially true for voting stock; stock which gives you voting rights in company decisions makes each stock one vote, so effectively whomever controls the majority of one stock gets that vote. However, various stock management policies on the part of the shareholder, brokerage firm or the issuing company can result in you owning fractional shares.
Perhaps the most common is a retirement account or other forward-planning account. In such situations, it's the dollar amount that counts; when you deposit money you expect the money to be invested in your chosen mix of mutual funds and other instruments. If the whole-shares rule were absolute, and you wanted to own, for instance, Berkshire Hathaway stock, and you were contributing a few hundred a month, it could take you your entire career of your contributions sitting in a money-market account (essentially earning nothing) before you could buy even one share. You are virtually guaranteed in such situations to end up owning fractions of shares in an investment account. In these situations, it's usually the fund manager's firm that actually holds title to the full share (part of a pool they maintain for exactly this situation), and your fractional ownership percentage is handled purely with accounting; they give you your percentage of the dividends when they're paid out, and marginal additional investments increase your actual holdings of the share until you own the whole thing. If you divest, the firm sells the share of which you owned a fraction (or just holds onto it for the next guy fractionally investing in the stock; no need to pay unnecessary broker fees) and pays you that fraction of the sale price.
Another is dividend reinvestment; the company may indicate that instead of paying a cash dividend, they will pay a stock dividend, or you yourself may indicate to the broker that you want your dividends given to you as shares of stock, which the broker will acquire from the market and place in your account.
Other common situations include stock splits that aren't X-for-1. Companies often aren't looking to halve their stock price by offering a two-for-one split; they may think a smaller figure like 50% or even smaller is preferable, to fine tune their stock price (and thus P/E ratio and EPS figures) similar to industry competitors or to companies with similar market capitalization. In such situations they can offer a split that's X-for-Y with X>Y, like a 3-for-2, 5-for-3 or similar. These are relatively uncommon, but they do happen; Home Depot's first stock split, in 1987, was a 3-for-2. Other ratios are rare, and MSFT has only ever been split 2-for-1. So, it's most likely that you ended up with the extra sixth of a share through dividend reinvestment or a broker policy allowing fractional-share investment.