# Half on a Double: public data guide

Canonical: https://halfonadouble.com
Data through: 2026-10-16 close
Publisher: Half on a Double

Half on a Double publishes end-of-day options-positioning reference levels for US stocks and ETFs.

## Reading the published values

- Close: the underlying's closing price, in US dollars per share.
- Delta neutral: the model's reference price associated with balanced aggregate delta.
- Gamma neutral: the model's reference price associated with neutral aggregate gamma.
- Gamma max: the model's reference price associated with peak aggregate gamma.
- Open interest: the number of outstanding option contracts, distinct from trading volume or shares.
- Max pain: the strike minimizing aggregate intrinsic payout. The nearest-expiration value and its expiry are separate from the all-expiration pooled value.
- Net GEX: signed whole-chain gamma exposure at the close, with calls positive and puts negative. GEX flip is a confirmed zero crossing; call and put walls are the largest side-specific GEX strikes. These are model conventions, not observed dealer inventory.
- Put/call open-interest ratio: put open interest divided by call open interest.
- Call-versus-put OI growth: percentage changes over one or five sessions. Positive call-minus-put growth gaps favor calls; negative gaps favor puts. Each side's daily contract change and the growth gap have separate historical surprise scores. These measure outstanding-contract balance, not IV skew or trade direction.
- Open-interest change z-score: today's contract change minus the mean of up to 252 preceding daily changes, divided by their sample standard deviation. Today is excluded; at least 200 prior changes are required. A value of +2 means the increase was two standard deviations above that ticker's recent norm.
- Advanced options: the same-date feed publishes selected ticker aggregates and daily average-IV history; contract-level arrays and option-pricing inputs are withheld. Its catalyst-intensity score combines equally weighted volatility-level, term-premium, activity and skew/shape groups. Correlated measurements are averaged within a group. The directional score summarizes relative positioning separately. Neither score is a probability, known event, price target or recommendation.
- Distance: (level − close) / close × 100. Retain its sign when quoting it; positive places the level above the close and negative below it.
- Absolute distance removes the sign. The historical distance rank is the percentage of up to 252 preceding valid sessions whose absolute distance was strictly smaller than today's; today is excluded and ties are not counted as closer.
- A cross records a change of side relative to a level between published sessions. It does not predict the next move.
- Forward cross outcomes are close-to-close returns after the labelled number of subsequent trading sessions. They are grouped by cross direction and include only events where gamma max was within 10% of the close on both crossing sessions.
- The order-statistic median interval has nominal coverage of at least 90% under independent observations. The confidence floor is its closest-to-zero bound, or zero when the interval spans zero. Cross windows can overlap, so neither is a formal coverage guarantee or forecast.

## Scope and limitations

Use the data-through date on each page, not the date you retrieve it. These are end-of-day observations, not live quotes. Missing values mean unavailable, never zero. Published levels depend on model assumptions and incomplete or imperfect market inputs. They do not reveal dealers' actual positions or guarantee support, resistance, or a profitable trade.

These documents publish definitions and selected displayed results. The calculation implementation, calibration, numerical procedures and internal inputs are proprietary and are not included. Do not infer a replication recipe from these summaries.

Quote the canonical page, ticker or screen, and data-through date together. The output is educational and descriptive, not investment advice. See [data and reuse](https://halfonadouble.com/data.md), [methodology and limitations](https://halfonadouble.com/methodology.md), and [disclaimer](https://halfonadouble.com/disclaimer.md).

## Explore

- [Daily screens](https://halfonadouble.com/screens.md)
- [Chart](https://halfonadouble.com/chart)
- [Learning guides](https://halfonadouble.com/learn)
- [Agent directory](https://halfonadouble.com/llms.txt)

The ticker Markdown documents cover the site's full-history, indexable pages. They contain a current snapshot, not the entire historical dataset.