Benn Eifert 🥷🏴‍☠️ Profile picture
Oct 24, 2022 8 tweets 2 min read Read on X
people asking a lot about the skew discussion from the letter. this thread should help.

the key thing is that skew tells you about the market-implied level of statistical covariance between an underlying asset's returns and the implied volatility of its fixed strike options
in an environment where fixed strike vol is falling when asset prices fall and rising when they rise, in order for a long skew position (long downside put, short upside call, dynamically hedged) to break even, the skew curve needs to be upward sloping!
this is because when you are long skew, you are short vanna: as the underlying asset falls, you get long fixed strike volatility exposure, and as fixed strike vol rises you get short exposure to the underlying asset
if spot falls and fixed strike vol drops, you get long vol and long delta and lose money on it; and you were paying theta for the privilege (assuming skew is inverted like normal in equity indices)
just because skew is at the 1st percentile of its own historical distribution doesn't mean you will make money owning it if it eventually reverts to more normal ranges; it may end up carrying sharply negative against you (as now)
another example of first order thinking almost never works in derivatives, need to understand the nuances of how the math works in a proper attribution framework in a portfolio that is losing you money 😅
low ain't cheap 🥷
fwiw this prompted my favorite incoming text message of the day 🥹☠️

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More from @bennpeifert

Dec 27, 2025
Let me explain in a little more detail what a martingale strategy is and why it's particularly susceptible to this kind of charlatanism and borderline fraud.

Let's say I have a coin flip bet, 50/50 heads/tails, heads I make $1 and tails I lose $1.
"fair coin" is about right, selling iron condors is a zero expected return trade at mid-market, actually negative expected return if you're crossing bid/ask spread at Captain Condor's size, but let's be generous
Captain Condor's "martingale" strategy is that every time he gets tails, he loses his bet size and doubles his bet size for the next coin flip. Every time he gets heads, he resets to his base sizing, bet $1.
Read 12 tweets
Dec 26, 2025
if your "quantitative model" says to bet the life savings of your investors that that S&P cannot move 30 basis points on one random day with 90,000 iron condors, you have the wrong idea of what a quantitative model is supposed to be
making a spreadsheet that says "this thing barely ever happens five times in a row", and using that to justify some insanely massive risky zero-edge trade after it just happened four times in a row, is batshit fucking crazy
there is ~zero statistical relationship between the incidence of one iron condor paying off today and the next one paying off tomorrow, just like the s&p being up today has ~zero statistical relationship with the s&p being up tomorrow
Read 8 tweets
Nov 2, 2025
Sam Altman is a fascinating new type of person -- someone who is transparently a sociopathic liar and grifter and immensely unlikeable to 99% of humanity, but within Silicon Valley tech bro circles is viewed as incredibly charismatic and visionary
not literally the only one (thiel, andreesen, elon)

just somewhat new to tech

used to be finance 1980s-2000s
Read 4 tweets
Aug 27, 2025
Good morning. I'm on a posting break but everyone is sending me this so just a brief explanation. 🖤

The headline is correct, but the implications are not. The VIX complex is very expensive on a relative basis right now and hedge funds are short it against other vol exposures.
VIX basis to at the money forward S&P volatility is very high, so volatility hedge funds are short VIX futures and long S&P forward volatility and variance against it
The VIX term structure is very steep (extremely high roll-down and volatility risk premium) so hedge funds are short it and short delta against it or long other volatility exposures against it
Read 6 tweets
Aug 19, 2025
Okay. I promised a quick thread on put/call parity after that poll yesterday, even though typically I like to stick to topics that aren't well covered in the public domain.

We'll start with the basic idea and then talk about nuances that make it not quite true (esp. for retail).
Put/call parity describes the fact that, if you can go long or short the underlying, whether an option is a call or a put doesn't really matter, it just affects its delta, or sensitivity to the underlying (which can be adjusted by holding a position in the underlying!)
In particular, the simple version of put-call parity says that owning the stock hedged with a long put option with strike K is effectively identical to owning a call option with strike K and holding the present value of K in cash.
Read 11 tweets
Aug 14, 2025
The people wanted a covered calls / option selling mega-thread, a one-click response to all the charlatans out there trying to farm retail investors.

Systematically, blindly selling options is a BAD IDEA. Underperforms owning equities by a lot. Let's go through why and how.
Okay. The starting point here is flows. Before 2010 or so, options markets were sort of a backwater. Risk premium was relatively high, so if you backtested simple option selling strategies like covered calls or cash-secured puts, they looked pretty good (see PUT INDEX, BXM INDEX)
Then pension fund consultants started to write white papers and pitch "equity like returns with lower risk via option selling" to their massive clients. And by 2012, tens of billions of dollars of institutional money started to flow into benchmark-oriented option selling...
Read 29 tweets

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