What is a stock split (reverse split)?
It was actually a reverse split meaning that every 10 shares you had became 1 share and the price should be 10x higher. - Citigroup in reverse split The chart just accounts for the split. The big dip is Googles way of showing from what price it split from. If you remember before the split the stock was trading around $4-$5 after the reverse split the stock became 10x higher. Just to clear it up a 1:2(1 for 2) split would mean you get 1 share for every 2 shares you have. This is known as a reverse split.  A 2:1(2 for 1) split means you get 2 shares for every 1 share you have. The first number represents the amount of shares you will receive and the second number represents how many shares you will be giving up.
During a stock split the only thing that changes is the number of shares outstanding.  Typically a stock splits to lower its price per share.  Sometimes if a company's value is falling it will do a reverse split where X shares will be exchanged for Y shares.  This is typically done to avoid being de-listed from an exchange if the price per share falls below a certain threshold, usually $1.  Again the only thing changing is the number of shares outstanding.  A 20 for 1 reverse split means for every 20 shares outstanding the shareholder will be granted one new share. Example X Co. has 1,000,000 shares outstanding for a price of $100 per share.  It does a 1 for 10 split.  Now there are 10,000,000 shares outstanding for a price of $10 per share. Example Y Co has 1,000,000 shares outstanding for a price of $1 per share.  It does a 10 for 1 reverse split.  Now there are 100,000 shares outstanding for a price of $10. Quickly looking at the news for ASTI it looks like it underwent a 20 for 1 reverse split.  You should probably look at your statements and ask your broker how the arithmetic worked in your case. Investopedia links for Reverse Stock Split and Stock Split When I log in to Schwab to look at these options it tells me there's only Adjusted Options available on these terms: Adjusted Options:   Multiplier: 100; Deliverable: 15 PTIE; Cash: ---- It does confirm your July Call quote price of $0.05 because the contract, though priced for 100 shares, will only deliver 15 shares.  Separately, looking at the company website for news there was a 7 for 1 Reverse Split announced on May 8, which is the culprit for this option adjustment and the seemingly nonsensical call price. The reason to do a stock split is to get the price of the stock down to an affordable range. If your stock costs $100,000 per share, you are seriously cutting in to the number of people who can afford to buy it. I can think of two reasons NOT to do a stock split. The biggest is, Why bother? If your stock is trading at a reasonable price, why change anything? It takes time and effort, which equals money, to do a stock split. If this serves no purpose, you're just wasting that effort. The other reason is that you don't want to drive your stock price down too low. Low prices are normally associated with highly speculative start-up companies, and so can give a wrong impression of your company. Also, low prices make it difficult for the price to reflect small changes. If your stock is trading at $10.00, a 1/2 of 1% change is 5 cents. But if it's trading at $1.50, a 1/2 of 1% change is a fraction of a penny. Does it go up by that penny or not? You've turned a smooth scale into a series of hurdles. Stock splits are typically done to increase the liquidity of stock merely by converting every stock of the company into multiple stocks of lower face value. For example, if the initial face value of the stock was $10 and the stock got split 10:1, the new face value of the stock would be $1 each. This has a proportional effect on the market value of the stock also. If the stock was trading at $50, after the split the stock should ideally adjust to $5. This is to ensure that despite the stock split, the market capitalization of the company should remain the same. Number of Shares * Stock Price = Market Capitalization = CONSTANT One way that is common is to show the value over time of an initial investment, say $10,000.  The advantage of this is that it doesn't show stock price at all, so handles splits well.  It can also take into account dividend reinvestment.  Fidelity uses this for their mutual funds, as can be seen here.  Another option would be to compute the stock price as if the split didn't happen.  So if a stock does a 2:1 split, you show double the actual price starting at that point. On Monday, the 27th of June 2011, the XIV ETF underwent a 10:1 share split. The Yahoo Finance data correctly shows the historic price data adjusted for this split.  The Google Finance data does not make the adjustment to the historical data, so it looks like the prices on Google Finance prior to 27 June 2011 are being quoted at 10 times what they should be.   Coincidentally, the underlying VIX index saw a sudden surge on the Friday (24 June) and continued on the Monday (27 June), the date that the split took effect.  This would have magnified the bearish moves seen in the historic price data on the XIV ETF. Here is a link to an article detailing the confusion this particular share split caused amongst investors.  It appears that Google Finance was not the only one to bugger it up.  Some brokers failed to adjust their data causing a lots of confusion amongst clients with XIV holdings at the time. This is a recurring problem on Google Finance, where the historic price data often (though not always) fails to account for share splits. You can argue that cash dividend is a kind of split as well by this logic. The stock price on ex-dividend gets a hit coincidental with the dividend to be paid, so one can argue that the investor has the same cash value on the day the dividend was paid as if it wouldn't be paid at all. However, for the company to distribute stocks instead of cash may be advantageous if they have low cash reserves but significant amount of treasury stocks, and the stocks are of high liquidity.  It is also a way for the company to release treasury stocks without diluting the current shareholders and creating taxable income to the company, that's an important factor to consider. This is in fact the real answer to your question. The main difference between split and stock dividend is that in split, the stock distributions proportions don't change. With stock dividend - they do. While the outstanding share proportions do not change, total proportions do, because of the treasury stocks being distributed. So company has less stocks in its vaults, but everyone else still has the same proportions of ownership. Compare this to split: company's treasury stocks would be split as well, and it would continue essentially sitting on the same proportion of stocks. That shift of treasury stocks to the outside shareholders - this is what makes it a dividend. A share of stock is a small fraction of the ownership of the company. If you expect the company to eventually be of interest to someone who wants to engineer a merger or takeover, it's worth whatever someone is willing to pay to help make that happen or keep it from happening. Which means it will almost always track the company's value to some degree, because the company itself will buy back shares when it can if they get too cheap, to protect itself from takeover. It may also start paying dividends at a later date. You may also value being able to vote on the company's actions. Including whether it should offer a dividend or reinvest that money in the company. Basically, you would want to own that share -- or not -- for the same reasons you would want to own a piece of that business. Because that's exactly what it is.