Quote from fvmn:
When why would the options with no trading volume at all (I literally mean 0 volume) move synchronically with their (relatively) heavy traded brothers? How can you explain it otherwise than market maker in action?
If there's zero volume in a strike, the market makers make their markets in that strike based on the IV of its "heavily traded brothers." But the IV in those "brothers" is set by supply and demand.
This should be obvious. Imagine a day when IBM stock doesn't move all day. On this day the 100 calls are .45 bid at .55. Imagine further that some big house comes in and buys those calls all day long - a total of 20,000 calls by the end of the day.
At the beginning, the market makers have a certain number they're willing to sell at their offer of .55. But do you think they're willing to sell an infinite number there? If so, they wouldn't be in business for long.
No, they'll sell a certain number at .55. When they've sold all they're willing to sell at .55, they'll raise their offer to .60. When they've sold all they're willing to sell at .60, they'll raise their offer to .65. When they've sold all they're willing to sell at .65, they'll raise their offer to .70.
Each time the 100 calls sell at the next higher price, the implied volatility jumps (remember in our example IBM stock is not moving). By the end of the day, those 20,000 buys will have driven IV significantly higher.
How else do you think implied volatility goes up and down? It's in response to supply and demand. Plain and simple.