Finding Mispriced Options    • 147
the near at-the-money (ATM) strikes were the most active because of the 
two far OTM options that traded; one’s price didn’t change at all, and the 
other went up by 1 cent. On a day in which the underlying stock fell, these 
calls theoretically should have fallen in price as well (because the K/S ratio, 
the ratio of strike price to stock price, was getting slightly larger). This just 
shows that sometimes there is a disconnect between theory and practice 
when it comes to options. 
To understand what is probably happening, we should understand 
something about market makers. Market makers  are employees at bro-
ker-dealers who are responsible for ensuring a liquid, orderly securi-
ties market. In return for agreeing to provide a minimum liquidity of 
10 contracts per strike price, market makers get the opportunity to earn 
the bid-ask spread every time a trade is made (I will talk about bid-ask 
spreads later). However, once a market maker posts a given price, he or 
she is guaranteeing a trade at that price. If, in this case (because we’re 
dealing with OTM call options), some unexpected positive news comes 
out that will create a huge rise in the stock price once it filters into the 
market and an observant, quick investor sees it before the market maker 
realizes it, the investor can get a really good price on those far OTM call 
options (i.e., the investor could buy a far OTM call option for 1 cent and 
sell it for 50 cents when the market maker realizes what has happened. 
To provide a little slack that prevents the market maker from losing too 
much money if this happens, market makers usually post prices for far 
OTM options or options on relatively illiquid stocks that are a bit unrea-
sonable—at a level where a smart investor would not trade with him or 
her at that price. If someone trades at that price, fine—the market maker 
has committed to provide liquidity, but the agreement does not stipulate 
that the liquidity must be provided at a reasonable price. For this reason, 
frequently you will see prices on far OTM options that do not follow the 
theoretical “rules” of options.
Bid-Ask
For a stock investor, the difference between a bid price and an ask price 
is inconsequential. For option investors, though, it is a factor that must 
be taken into consideration for reasons that I will detail in subsequent