# Why dealers hedge

**DL-01 · Dealer Logic · Core**

**Lesson question:** Why might an option trade create a separate underlying trade?

Original fictional examples; educational writing, not live market data, orders or production approval.

## By the end

- Explain the mechanism in the lesson question.
- Reproduce the worked comparison and recognize its failure case.

A dealer can provide an option to a customer without wanting to retain all of its directional exposure. Hedging changes the risk of the total book; it does not eliminate every risk or explain every market move. Begin with inventory rather than a theory that dealers control price.

## Understand the mechanism

If option-book Delta is equivalent to +1,200 shares, a −1,200-share hedge neutralizes that local exposure. The desk can use shares, suitable futures or other options. The best vehicle depends on the underlying and the residual risks.

Inventory must be aggregated. A customer buying calls from one desk does not establish the net position of every dealer after other trades, strikes and expiries are included.

## Walk through the process

Identify the instrument and sensitivity units. Establish whether the inventory sign is known or assumed. Calculate a target hedge and compare it with the hedge already held.

Desks can internalize offsetting trades, hedge at thresholds or retain permitted risk. Gross option volume is therefore not a direct measurement of immediate futures flow.

## Evidence boundary

The arithmetic is original conditional teaching material, not a measurement of current dealer positions. The cited Cboe research is historical product-specific evidence, not a live inventory feed. Model outputs should remain distinguishable from observed market facts.

## A worked example

A fictional desk has +1,200 share-equivalents of option Delta and holds −1,200 shares. Another trade reduces its option Delta to +900. Leaving the old hedge unchanged makes the combined book −300.

Buying 300 shares restores local neutrality. The adjustment is not buying 900: that is the new option exposure, not the difference between current and desired hedges. The chart shows the two inventory observations.

## Graph: Why dealers hedge—worked comparison

**Horizontal:** Inventory observation  
**Vertical:** Option Delta (share-equivalents)

Fictional data from the written example. The chart organizes the comparison; its shape is not a forecast.

Complete numerical data are embedded in `scripts/dealer-logic/DL-01.js` and displayed as an accessible table in the HTML lesson.

## What would invalidate the reading?

Gross volume without signed net inventory cannot establish the hedge direction. A seemingly precise calculation can be backward when its assumed ownership sign is wrong.

## Check your understanding

### What adjustment restores neutrality after option Delta changes from +1,200 to +900 while the hedge remains −1,200?

**Answer:** Buy 300 shares.

**Why:** Combined Delta is −300 before the adjustment.

### What is the critical failure to avoid?

**Answer:** Gross volume without signed net inventory cannot establish the hedge direction. A seemingly precise calculation can be backward when its assumed ownership sign is wrong.

**Why:** Explain this risk before treating the example as a decision rule. A correct calculation does not guarantee a favorable market outcome. **Critical risk check.**

## Takeaway

Return to the question: Why might an option trade create a separate underlying trade? State the observed facts, the assumptions and the failure condition separately.

## References and provenance

The cited references support definitions and conventions. The teaching prose, tickets and numerical scenarios are original; they are not attributed as historical market observations.

- [OIC Greeks](https://www.optionseducation.org/advancedconcepts/understanding-options-greeks)

- [Cboe 0DTE positioning study, May 2025](https://www.cboe.com/insights/posts/0-dt-es-decoded-positioning-trends-and-market-impact)