OAP 050: Is The Stock Market Random Or Predictable? The Final Debate On Efficient Markets

Options Trading
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One of the foundational elements of my personal trading style with options is the belief that the stock market is random. Random meaning that we can't gain an edge picking a direction. And for years, this assumption has been more or less accepted by the public and academia.

In the last couple months, the theory or hypothesis around random financial markets has repeatedly been challenged, which is a good thing. A countless number of people have tackled the issue and published their findings on random market behavior. I wish I could link them all up here, but it's just not possible nor realistic. Therefore, my goal on today's show is simply to present what I believe to be the best research on the topic of market efficiency and predictability.

Admittedly, I scheduled this show as a follow-up to Show 49 where we backtested 15 different option buying strategies during the last market crash. And the reason is that I wanted you to recognize how much "perfect timing" had an impact on the results of that case study. In Show 49, we only backtested the put buying strategies for two years assuming you were 100% right in calling the impending market crash.

If you expanded the timeline out to 3 years on either end - i.e. you're not a market wizard and can't time the crash precisely, then each and every scenario lost money. In fact, each backtested put buying strategy only made money during Sep & Oct of 2008 at the height of the collapse. During all of 2007, you would have lost on average 56% of your capital waiting for the crash to happen.

Be honest with me now; how likely is it that you would have actually held through a 56% drop in your account balance before you called it quits? And that was assuming you had near perfect market timing! Still, the traders who sold options didn't try to time the market, eventually won. Sure, they may have experienced a draw down in 2008 if there were not positioned correctly, but even still they would have made money trading through the crash.

As you listen to the show, I want to challenge you to ask yourself the following pressing questions about investing; Is the stock market random? If it is, why should we care so much about picking a random direction? If it isn't, and indicators are present to predict future moves, can I even uncover the non-random patterns? How much time or money would it take to profit under the assumption of randomness vs. non-randomness? What trading strategies fit my personal style the best?

Key Points from Today's Show:

Background Hypotheses and Theories

  • Time Series Hypothesis — everyone in the market has more or less a different timeline that they are trading on; day traders, minute chart traders, weekly traders, monthly traders, yearly traders, etc.
  • Random Walk Theory — the stock price changes have the same distribution and are independent of each other, so yesterday's move cannot be used to predict it's future movement tomorrow.
  • Efficient Market Hypothesis — the main facet of Random Walk that supports the idea that all information is already priced into the security or the stock price. There is no edge that can be gained when you get news; as soon as news is released to the market it is disseminated and the news re-prices the value of the stock.

Research and Findings

  • Mean reversion study by Lo and MacKinlay (1999): suggests that short run stock correlations are not zero — not a high correlation, but not zero.
  • Concludes that the short-run price movement of a stock is not completely independent of each individual day, showing that Random Walk is not completely true.
  • Also, prove that short run stock prices can gain momentum, due to investors "jumping on the bandwagon", leading to several consecutive periods of the same direction of price movement.
  • However, in the long run, they do see correlations that are much closer to zero, if not at zero, for major markets, suggesting that the patterns normalize in the long term.


  • In the short term, you can see price movements start to trend or “gain momentum” in either direction. In the longer term, these trends are more or less averaged out.
  • Any patterns or anomalies are more reliable than random during the short term and become less and less reliable in the long term as they do normalize.
  • Be aware that with data mining, if you churn data enough, you are eventually going to find predictive patterns somewhere.
  • If you had to pick, the markets are random — 95% of the market is random in nature. However, in the shorter term periods the momentum or "bandwagon indicators" do actually have some predictive power.
  • Does technical analysis work? Yes. In a short term and a small contained set of parameters. Is the market 100% efficient and random? No. It is definitely more random than not, but there are inefficiencies and non-random aspects to the market that you have to be aware of.

Links Mentioned in this Episode:




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Free Options Trading Courses:

  • Options Basics [20 Videos]Whether you're a completely new trader or an experienced trader, you'll still need to master the basics. The goal of this section is to help lay the groundwork for your education with some simple, yet important lessons surrounding options.
  • Finding & Placing Trades [26 Videos]Successful options trading is 100% dependent on your ability to find and enter trades that give you an "edge" in the market. This module helps teach you how to scan properly for and select the best strategies to execute smarter option trades each day.
  • Pricing & Volatility [12 Videos]This module includes lessons on mastering implied volatility and premium pricing for specific strategies. We'll also look at IV relativeness and percentiles which help you determine the best strategy to use for each and every possible market setup.
  • Neutral Options Strategies [7 Videos]The beauty of options is that you can trade the market within a neutral range either up or down. You'll learn to love sideways and range bound markets because of the opportunity to build non-directional strategies that profit if the stock goes up, down or nowhere at all.
  • Bullish Options Strategies [12 Videos]Naturally everyone wants to make money when the market is heading higher. In this module, we'll show you how to create specific strategies that profit from up trending markets including low IV strategies like calendars, diagonals, covered calls and direction debit spreads.
  • Options Expiration & Assignment [11 Videos]Our goal is to make sure you understand the logistics of how each process works and the parties involved. If you don’t feel confident in the expiration processes or have questions that you just can't seem to get answered, then this section will help you.
  • Portfolio Management [16 Videos]When I say "portfolio management" some people automatically assume you need a Masters from MIT to understand the concept and strategies - that is NOT the case. And in this module, you'll see why managing your risk trading options is actually quite simple.
  • Trade Adjustments/Hedges [15 Videos]: In this popular module, we'll give you concrete examples of how you can hedge different options strategies to both reduce potential losses and give yourself an opportunity to profit if things turn around. Plus, we'll help you create an alert system to save time and make it more automatic.
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PDF Guides & Checklists:

  • The Ultimate Options Strategy Guide [90 Pages]: Our most popular PDF workbook with detailed options strategy pages categorized by market direction. Read the whole guide in less than 15 mins and have it forever to reference.
  • Earnings Trading Guide [33 Pages]: The ultimate guide to earnings trades including the top things to look for when playing these one-day volatility events, expected move calculations, best strategies to use, adjustments, etc.
  • Implied Volatility (IV) Percentile Rank [3 Pages]A cool, simple visual tool to help you understand how we should be trading based on the current IV rank of any particular stock and the best strategies for each blocked section of IV.
  • Guide to Trade Size & Allocation [8 Pages]Helping you figure out exactly how to calculate new position size as well as how much you should be allocating to your each position based on your overall portfolio balance.
  • When to Exit/Manage Trades [7 Pages]Broken down by option strategy we'll give you concrete guidelines on the best exit points and prices for each trade type to maximize your win rate and profits long-term.
  • 7-Step Trade Entry Checklist [10 Pages]Our top 7 things you should be double-checking before you enter your next trading. This quick checklist will help keep you out of harms way by making sure you make smarter entries.

Real-Money, LIVE Trading:

  • IWM Iron Butterfly (Closing Trade): Exiting this IWM iron butterfly options trade gave us a $1,100+ profit after pinning the stock price one day before expiration at the peak of our spread.
  • CMG Iron Condor (Opening Trade): I just recorded my live trading platform (and real money account) as I walked through the process of entering a new iron condor trade in CMG stock. Inside you'll see me analyze, price and fill the trade in real-time.
  • APC Strangle (Closing Trade): Took about $150 out of this small APC strangle trade even after the stock moved completely against our short call strikes this month. But as always, implied volatility always trumps direction and because IV went down, the value of this spread dropped more-so than the impact of the directional move higher.
  • IYR Call Credit Spread (Adjusting Trade): This adjustment is good for 2 reasons. First, it reduces the overall risk in the trade if IYR continues to move higher. Second, it still leaves room for the stock to fall back down into our new profit window.
  • XHB Straddle (Closing Trade): We were able to bank a $120 profit early in the March expiration cycle for our XHB straddle with the stock trading right in the middle of our expected range.
  • AAPL Call Calendar (Opening Trade): Look behind the scenes as I use our new watchlist software to filter quickly and find this AAPL call calendar spread trade during overall low implied volatility in the market.
  • COF Strangle (Adjusting Trade): Here I recorded my live trading screen (and real money account) showing you the entire thought process we used to make an adjustment to my current short strangle in COF to reduce risk.
  • GDX Strangle (Opening Trade): With gold's high IV we are getting into a new strangle with a 70% chance of success and a decent credit for selling option premium.
  • IBB Iron Condor (Closing Trade): Today we're exiting an iron condor we traded in IBB for a $142 profit. Inside you'll see me analyze the exit price and fill the trade in real-time.

Thank You for Listening!

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About The Author

Kirk Du Plessis

Kirk founded Option Alpha in early 2007 and currently serves as the Head Trader. In 2018, Option Alpha hit the Inc. 500 list at #215 as one of the fastest growing private companies in the US. Formerly an Investment Banker in the Mergers and Acquisitions Group for Deutsche Bank in New York and REIT Analyst for BB&T Capital Markets in Washington D.C., he's a Full-time Options Trader and Real Estate Investor. He's been interviewed on dozens of investing websites/podcasts and he's been seen in Barron’s Magazine, SmartMoney, and various other financial publications. Kirk currently lives in Pennsylvania (USA) with his beautiful wife and three children.