Market Data Logo
Last Update: March 20, 2024

Understanding Differences in Implied Volatility and Greeks Between Broker Platforms

Options trading is a sophisticated endeavor, involving numerous variables and calculations to guide traders in their decision-making processes. Among the most pivotal of these calculations are implied volatility (IV) and the Greeks (Delta, Gamma, Theta, Vega, and Rho), which offer insights into the price sensitivity of options to various factors. However, traders often encounter discrepancies in these values when comparing data across different broker platforms, including the Market Data API and Sheets Add-on. Let’s explore the reasons behind these differences.

Exchanges and the Absence of Standard Calculations

First and foremost, it’s crucial to understand that stock and options exchanges do not calculate or provide Greeks and IV as part of their official data feeds. There is no such thing as an “official” value for IV and Greeks. This means that every trading platform, brokerage, or data provider must undertake the calculation of these values independently, using whatever methods they feel most appropriate. The absence of a standardized approach leads to the first layer of variability in the Greeks and IV observed by traders.

Diversity in Options Pricing Models

The core of understanding IV and Greeks’ variability lies in the options pricing models employed. Several models exist, each with its strengths and contexts of applicability:

  • Black-Scholes-Merton Model: Developed in the early 1970s, the Black-Scholes-Merton Model revolutionized options trading with its mathematical elegance and simplicity. It assumes a constant volatility and a lognormal distribution of stock prices over time, excluding the payment of dividends. Its widespread adoption is due in part to its straightforward approach to European option pricing, where options cannot be exercised before expiration.
  • Heston Model: Another significant model is the Heston model, which introduces stochastic volatility to address one of the main limitations of the Black-Scholes-Merton Model: the assumption of constant volatility. By allowing volatility to fluctuate, the Heston model offers a more realistic depiction of market conditions, making it valuable for pricing derivatives in volatile markets.
  • Binomial Model: The binomial model offers a more versatile approach to options pricing, accommodating scenarios with dividends and American options, which can be exercised at any time before expiration. This model visualizes an option’s life as a series of discrete time steps or nodes, each representing possible future movements in the underlying asset’s price. The flexibility to adjust the number of periods in the model makes it particularly useful for examining the detailed behavior of an option across its life.
  • Bjerksund-Stensland Model: Specifically tailored for American options, which may be exercised before expiration, the Bjerksund-Stensland Model is an improvement designed to account for the optionality of early exercise. This model is particularly adept at handling options on dividend-paying stocks, where the decision to exercise early can significantly impact valuation.
  • Monte Carlo Simulations: Unlike the other models, Monte Carlo simulations do not follow a specific formulaic approach to pricing. Instead, they use random sampling to generate a range of possible outcomes for an option’s price, taking into account the stochastic nature of the underlying asset’s price and volatility. This method is highly flexible and can be adapted to various complex instruments and scenarios, though it requires significant computational resources.
  • Local Volatility Models: These models, such as the one developed by Dupire, allow for the volatility surface to vary with both the price of the underlying asset and time. Local volatility models are used to calibrate market data and can provide a detailed view of how market participants’ expectations of volatility change across different strike prices and expirations.

Each of these models brings a unique perspective to options pricing, reflecting the complexity and diversity of financial markets. The choice of model can significantly influence the calculated values of IV and the Greeks, leading to the variations observed across different trading platforms and data providers. Understanding the foundational assumptions and applications of each model helps traders and analysts better interpret the data they rely on for making informed decisions.

Impact of Variable Inputs on Options Pricing Models

Even when employing the same pricing model, the outcomes of options calculations can significantly diverge across different platforms or data sources due to variations in the inputs used. These inputs are fundamental to the models’ calculations, influencing everything from implied volatility (IV) to the Greeks. Understanding these variables is crucial for traders looking to navigate the differences they encounter in options pricing across broker platforms.

Critical Variables and Their Variability

  • Risk-Free Interest Rate: The choice of risk-free rate is pivotal in options pricing, affecting the discount rate used in models. However, there’s no single universally accepted risk-free rate. Some platforms might use Treasury Bills (T-Bills), considering their short maturity as a close approximation of a “risk-free” asset. Others might opt for Treasury Bonds with a maturity that matches the expiration of the option for longer durations or the Secured Overnight Financing Rate (SOFR) as a benchmark for the cost of borrowing cash overnight collateralized by U.S. Treasury securities.
  • Dividend Yield: Dividends impact the value of options, particularly for models pricing American options where early exercise may be optimal ahead of dividend payouts. Platforms differ in how they project dividend yields – some use the trailing 12 months to estimate future payouts, while others might look at forward 12 months’ projected dividends. Additionally, the treatment of extraordinary dividends can vary, with some models excluding them from calculations due to their non-recurring nature.
  • Volatility: Perhaps the most critical input for IV calculations, volatility can be estimated in various ways. Historical volatility, based on past price movements, provides one perspective, while implied volatility looks forward, derived from market prices of options themselves. The choice and calculation methodology for volatility can lead to significant differences in IV across platforms.
  • Time to Expiration: The precise measurement of an option’s time to expiration can vary, with some platforms calculating down to the hour of expiration, while others might use a more generalized approach. This seemingly minor difference can impact the sensitivity of an option’s price to the passage of time, particularly as expiration approaches.
  • Underlying Asset Price: While it might seem straightforward, the source of the underlying asset’s price can introduce variability. Real-time versus delayed quotes, the selection of which exchange’s prices to use, or the method for calculating an average price from multiple sources can all result in different inputs for the same option on different platforms.

The interplay of these inputs in options pricing models underscores the complexity and nuanced nature of calculating IV and the Greeks. Traders and investors must be aware of these variables and how they are applied on the platforms they use to make informed decisions and understand the potential for variability in the data they rely on.

Broker-Specific Models and Calculations: A Look Behind the Scenes

When it comes to calculating options pricing, including implied volatility (IV) and Greeks, there’s no one-size-fits-all solution across broker platforms. Each broker might choose a different path, picking models that best suit their needs. Here’s why not all platforms will show you the same numbers:

  • Model Selection: Brokers have their own preferences or strategies, leading them to favor one model over another. This choice impacts how they calculate everything related to options, from IV to Greeks. For instance, while one platform might lean towards the Black-Scholes-Merton model for its simplicity, another might prefer the flexibility of the Binomial model for its ability to account for dividends and early exercise of American options.
  • Customization and Adjustments: Beyond just picking a model, brokers often tweak them. These customizations can significantly alter the calculations, making them unique to that platform.
  • Update Frequency: Calculating IV and Greeks can be heavy on the computational side. To manage resources, brokers have to make a call on how often to update these values. Some might update the data every 15 minutes, balancing the need for accuracy with system performance. Others, especially those offering desktop applications, allow calculations to run client-side, updating every second (or with every price tick) since it doesn’t burden their servers. This difference in update frequency can explain why you might see more current data on one platform compared to another.

The takeaway? If you’re seeing different numbers for IV and Greeks on different platforms, it’s not just about data quality or delays. It’s often about deliberate choices made by each broker, from the models they use to how often they update the calculations. Understanding the reason behind these differences can help you be more effective in your trading strategy.

Data Sourcing Variability at Market Data

At Market Data, our commitment to providing comprehensive data involves sourcing information from various upstream providers. Given that each provider may utilize different models and inputs for their calculations, IV & Greeks consistency across data requests cannot be guaranteed. This diversity reflects the broader market’s complexity and underscores the importance of understanding the underlying calculations behind the data provided.

This detailed exploration into the reasons behind the variability in IV and Greeks across different platforms and data providers aims to equip traders with the knowledge to navigate these differences effectively. By appreciating the complexity and the lack of a “one true value” when it comes to Greeks and IV in options trading, users can make more informed decisions.

Why You Might Want to Do Your Own Math

The bottom line is that if you’re seeing different numbers for things like implied volatility (IV) and Greeks across different trading platforms, it’s not just you. It’s because everyone’s using different methods and assumptions to crunch those numbers. This can be a bit of a headache if you’re trying to make precise trading decisions.

Consider doing the calculations yourself. Pick a method that makes sense to you, and stick with it. This way, you can keep your numbers consistent, which can be helpful for making solid trading choices. You don’t need to be a quant to do this; there are plenty of libraries and resources to help you get started.

Keeping your calculations in-house doesn’t mean you should ignore what the Market Data API or the trading platforms show. But, blending their info with your own calculations might give you the best of both worlds. Happy trading!

On this page
    Add a header to begin generating the table of contents
    Share this article
    Comments & Questions
    Shopping Basket