Quote from MasterAtWork:
I'm sorry Dmo, but you're still looking at short term options. The way you analyze datas is biased because you don't count roll overs and already closed positions. Be careful it's implied in you comment that people hold the positions to the maturity. It's wrong.
Don't you think that skew can be related there will always be an additional interest by rolling over a short call, not true with puts? (same volatility, same rates...)
Would you disagree that skew can be related to the fact that 12 points (your example) represent 1% ATM, will represent 1,1% at 1100 and 0,92% at 1300. So the market forestalled what "tomorrow" price is today worth?
Skew can be related with demand and supply...doesn't mean for portfolio insurance, just as bets. Doesn't it?
Well of COURSE the skew is related to supply and demand. That's ALL the skew is. It is a living, breathing indicator of the supply/demand for options at lower strikes vs. the supply/demand for options at higher strikes.
Since the vast majority of options that trade at lower strikes are puts and the vast majority of options that trade at higher strikes are calls, the skew is a direct reflection of the supply/demand for puts vs the supply/demand for calls. That's it. It is nothing else.
Let's look at the S&P500, since that skew is the most stable and consistent one. I've attached a screenshot showing the settlements of the September E-mini options as of yesterday. The futures settled at 1282.
Look at the lowest strike on this screenshot - the 1235. It settled at an IV of 19.71%. The next higher put (the 1240) settled at an IV of 19.47%, the next higher at 19.37%, the next higher at 19.15%, and so on. The highest strike shown - the 1320 call - settled at an IV of 16.04%.
The pattern is perfect. Without exception, every strike settled at an IV higher than the strike above, and lower than the strike below.
What does that mean? It is beyond argument or discussion that there is more demand for the lower strikes than for the higher strikes. That's what this shows in black and white.
So having established that basic fact, the next question is, "why? Why is there so much greater demand for options at the 1235 strike, than for options at the 1320 strike?"
In his typically succinct fashion, Atticus says "portfolio insurance," and that's the bottom line. In my typically wordy fashion, I'll elaborate.
At each strike, compare the volume of puts vs the volume of calls. You'll notice that below the money at almost every strike, more puts trade than calls. At the 1240 strike is 393/3, at the 1245 strike it's 158/13, at the 1250 strike it's 1483/151.
Now look at the above-the-money strikes, where more calls trade than puts. At the 1315 strike, it's 262 calls/35 puts. At the 1310 strike, 1059/9. At the 1305 strike, 183/70 and at the 1300 strike, 1624 to 200.
So the greater demand for options at the low strikes such as 1240 really reflects a greater demand for puts. The anemic demand for options at the 1315 strike really reflects low demand for calls.
So why are option traders so much more anxious to buy puts than calls? Again, "portfolio insurance." I can't prove anything past this point, but it just seems obvious common sense that a huge majority of people are net long stocks - far more than are net short stocks - and that accounts for the greater demand for puts as protection.
There's a little more to it than that but I have to take off for the day. Maybe later we can get into discussing a deeper reason for the skew. But it too is just an offshoot of the basic concept of options as portfolio insurance.