The Cost of a Free Lunch: Evidence from U.S. Derivatives Markets

The Cost of a Free Lunch: Evidence from U.S. Derivatives Markets

Derivatives Market Anomalies Uncovered in US Markets

Section 1 – What happened?

A recent study has revealed an intriguing anomaly in the US derivatives markets, specifically in the S&P 500 and Russell 2000 options. Researchers have found that the put-call parity, a fundamental concept in finance, is not always upheld in practice. Put-call parity is a theoretical relationship between the prices of put and call options that should be zero when calculated correctly. However, the study discovered that the actual cost of implementing this parity is not zero, but rather a non-trivial amount that varies over time. This discrepancy is attributed to daily settlement, margin, and finite capital requirements, which expose arbitrageurs to significant risks.

Section 2 – Background & Context

Put-call parity is a cornerstone of derivatives pricing theory, and its breakdown has significant implications for market participants. The study used minute-level data on National Best Bid and Offer (NBBO) prices for S&P 500 and Russell 2000 options to extract option-implied discount factors and compare them with the Overnight Indexed Swap (OIS) curve. This allowed the researchers to construct an annualized carry gap, which measures the difference between the theoretical and actual costs of implementing put-call parity. The study's findings have far-reaching implications for traders, investors, and financial institutions that rely on derivatives markets.

Section 3 – Impact on Swiss SMEs & Finance

While the study's findings are specific to the US derivatives markets, they have broader implications for the global financial landscape. Swiss SMEs and financial institutions that engage in derivatives trading may need to reassess their risk management strategies and adjust their expectations for returns. The study's results suggest that the costs of implementing put-call parity can be significant, and market participants may need to factor these costs into their investment decisions. Furthermore, the study's findings may have implications for regulatory policies and market infrastructure, potentially leading to changes in the way derivatives markets are designed and operated.

Section 4 – What to Watch

The study's results are likely to spark further research into the complexities of derivatives markets and the implementation of put-call parity. Market participants and regulators will be watching to see how these findings are incorporated into market practices and policies. Investors and traders will need to carefully evaluate the costs and risks associated with derivatives trading and adjust their strategies accordingly. As the study's authors note, the carry gap is an "implementation wedge invisible in price space but systematic in carry space," highlighting the need for a deeper understanding of the underlying dynamics of derivatives markets.

Source

Original Article: The Cost of a Free Lunch: Evidence from U.S. Derivatives Markets

Published: April 21, 2026

Author: Useong Shin

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Disclaimer: This article is for informational purposes only and does not constitute financial advice. Consult a licensed financial advisor before making investment decisions.