Your total Vega number is probably lying to you
If you run a multi-expiry options book and you're looking at one total Vega number, that number is probably lying to you.
Here's why.
A one-month implied vol can swing around in a huge range. A one-year implied barely moves by comparison. So a dollar of Vega in the front and a dollar of Vega in the back are not the same risk at all. They don't move together. They react to different things. They shift on different timeframes.
Add them up raw and you get a number that feels precise and means almost nothing.
You might think you're roughly flat vol when you're actually very long the front and short the back. Or the other way around. Same total Vega on the risk sheet. Two completely different exposures in real markets.
What desks do is weight each expiry before adding it in. More weight to the reactive short end. Less weight to the sleepy long end. Once you weight it, you get one honest number for whether you're really long or short implied vol.
The base case weighting is 1/sqrt(T). Which means three-month vol moves roughly double one-year vol. Front-month vol moves roughly twice again. So a dollar of front-month Vega carries several dollars of vol risk in weighted terms. The raw number understates the exposure by a factor tied to the expiry.
For me, until you weight it, you don't actually know your vol exposure. You just think you do.
The reason this matters is that vol regimes shift on the front end long before they shift on the back. When the market cracks, front-month vol moves first, hardest, and fastest. Long-dated vol barely twitches until the move is confirmed. If your position sheet is heavy short front-month Vega and long back-month Vega, an unweighted total Vega of zero disguises the fact that you're about to get run over on any vol event.
The weighted number tells you the truth. The raw number gives you a false sense of security.
This is the kind of institutional plumbing that separates traders who last from traders who blow up on the first vol event. The Greek you see on the screen is training wheels. The weighted Greek is what the desks actually manage.
If you'd like to know more about the framework I built across 20 years on bank options desks, check the link below.
A book built on unweighted Greeks might survive a low-vol regime. It won't survive a regime change. That's the difference between a book that earns for years and a book that lasts a quarter.
If you want to skip the masterclass and jump straight into our course, the Options Insight Advantage, this is the link.
Imran
Disclaimer (Your Gains & Losses, Your Responsibility): This content from Options Insight LLC (“Options Insight”) is for educational purposes only and does not provide individual investment advice or recommendations, nor should it be considered an offer to buy or sell any security. All information is general and not tailored to your specific objectives, financial situation, or risk tolerance. Employees of Options Insight may hold positions in the assets discussed. While we use sources believed to be reliable, we are not responsible for errors, omissions, or losses resulting from reliance on this content. Always consult a licensed investment professional.
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