Quadruple Witching, Concentrated Expiry Raises Volatility

TL;DR

• Quadruple witching occurs when index futures, index options, and single-stock options expiries overlap, concentrating liquidity and position rollovers.
• Position unwinds and changes in delta hedging around expiry can amplify short-term price volatility.

What is quadruple witching

Quadruple witching is an informal term for the simultaneous expiry of major derivatives at a specific time. In Korean markets, when index futures, index options, single-stock options, and single-stock futures expire together, market participants often call it "quadruple witching." On that day, liquidation, rollovers, and option exercises can cause trading to cluster more than usual.

Why volatility rises

The main drivers are as follows.

1) Position unwinds and rebalancing: Payouts are determined by expiry and strike, so profit-taking and stop-loss orders can occur simultaneously. Large orders concentrated on one side can move prices sharply.

2) Market maker delta hedging: Sellers of options hedge exposure to the underlying. As expiry approaches and option deltas shift rapidly, hedge sizes change quickly, increasing buy or sell demand in the underlying.

3) Liquidity thinning and slippage: Large expiry-related orders arriving at the same time make the order book thin, so identical volumes have larger price impact.

Common misconceptions

• "Quadruple witching always causes a crash." That is exaggerated. Expiry can raise volatility, but the direction depends on position composition. Prices can also pin near specific strikes.

• "Option expiry means institutions manipulate the market." Institutions and market makers hedge to manage risk, and while hedging can influence markets, it does not imply manipulation.

Delta hedge impact, a simplified numerical example

Below is a simplified hypothetical example. Actual numbers differ by exchange and broker, so check with your broker for current specs.

Assumptions:

• Sold a total of 1,000 call contracts (100 underlying shares per contract). That equals 100,000 underlying shares.
• Before expiry the call delta is 0.5 and the underlying price is 100 won.

Initial hedge requirement = 100,000 shares × 0.5 = buy 50,000 shares

If the price rises to 105 won and the option delta increases to 0.7
Additional hedge requirement = 100,000 shares × 0.7 - 50,000 shares = buy 20,000 more shares

As a result, the market maker must buy an additional 20,000 shares due to delta change. If that additional buying pushes the price further, delta changes again and further buys or sells can follow in a chain. This mechanism can amplify short-term volatility.

Practical notes

• Monitoring volume and bid-ask spread changes before and after expiry helps identify elevated volatility risk.
• The example numbers and simple model are for illustration; real markets include fees, slippage, position distribution, and other factors. Check brokers or the exchange for specific contract units and current details.

This article is for information only and is not investment advice.