Game Theory & Stock Trading: Why the Simplest Strategy Often Wins
•By Maher Alias
Artikel ini juga tersedia dalam Bahasa Melayu
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Imagine a tournament where hundreds of strategies compete against each other - some cunning, some aggressive, some incredibly complex. Who wins? Not the smartest or most sophisticated strategy. Instead, the simplest and most honest one.
This is not mere theory. This is an actual finding from game theory, proven through computer simulations by political scientist Robert Axelrod in the early 1980s. And what makes it even more fascinating is that the same principles can be applied to the world of stock trading and investing.
In this article, we will explore what game theory is, how the "Tit for Tat" strategy became the champion in Axelrod's experiment, and most importantly - how you can use game theory principles to become a smarter investor and trader on Bursa Malaysia and global markets.
Game theory is a branch of mathematics and economics that studies how individuals make strategic decisions when the outcome of their decisions depends on the actions of others.
The concept was first formally introduced by John von Neumann and Oskar Morgenstern in their book Theory of Games and Economic Behavior (1944). Later, John Nash introduced the concept of Nash Equilibrium in 1950 - a point of balance where no player can improve their outcome by unilaterally changing their strategy.
In the context of the stock market, the "players" are investors, traders, financial institutions, and market makers. Their "game" involves decisions to buy, sell, or hold a particular stock. And every decision made by one person affects the stock price - which in turn influences the profits or losses of other investors.
This is what makes the stock market a perfect "game" for game theory analysis.
To understand game theory, you need to understand its most fundamental concept - the Prisoner's Dilemma.
Imagine two suspects arrested by police. They are interrogated separately and given a choice:
Logically, the "rational" choice for each individual is to betray - because regardless of what the other person does, betraying always yields a better outcome for yourself. But when both think this way, they both end up with a worse outcome than if they had cooperated.
This happens every day in the stock market. When many traders panic and rush to sell (defect), prices crash and everyone loses. If they "cooperated" and stayed calm, the market would remain stable and everyone would benefit.
In the early 1980s, Robert Axelrod from the University of Michigan organised an epic computer tournament. He invited experts in game theory, mathematics, computer science, economics, and psychology from around the world to submit their strategies.
Each strategy would face every other strategy in an iterated Prisoner's Dilemma game - not once, but hundreds of rounds. The question: which strategy would accumulate the most points overall?
15 strategies were submitted in the first tournament. Some were highly complex, some tried to exploit opponents' weaknesses. But the winner was the simplest strategy - just 4 lines of code.
The winning strategy was submitted by Anatol Rapoport, a mathematician. It was called Tit for Tat and its rules were remarkably simple:
That's it. If your opponent cooperated, you cooperate. If your opponent betrayed, you betray. Then if your opponent returns to cooperation, you also return to cooperation.
Axelrod then held a second tournament. This time, 63 strategies were submitted - many specifically designed to defeat Tit for Tat. The result? Tit for Tat won again.
Axelrod identified four properties that made Tit for Tat so successful:
Most surprisingly, strategies that tried to be "smarter" than Tit for Tat - those that tried to exploit or manipulate opponents - almost all failed in the long run.
Nash Equilibrium is a state where no player in a "game" can improve their outcome by changing their own strategy, as long as other players maintain their strategies.
In the stock market, Nash Equilibrium occurs when a stock price reaches a point of balance - where buyers and sellers are balanced, and no investor has a strong incentive to change their position.
Imagine two large institutional investors each holding a significant amount of Company X shares:
At equilibrium, both choose to hold - because unilaterally changing strategy would only hurt them.
This explains why certain stocks remain stable at particular levels - there is a balance between buying and selling pressure that reflects Nash Equilibrium.
In the stock market, momentum traders follow the current trend - buying stocks that are rising. Contrarian traders do the opposite - buying when others are selling.
From a game theory perspective, this is a game between two groups. If too many traders follow momentum, the market becomes overvalued and prone to correction. If too many become contrarian too early, they bear losses while the trend remains strong.
Tit for Tat Application: Follow the trend (cooperate with the market), but respond immediately when there are reversal signals (retaliatory). Do not stubbornly hold a position that is clearly losing.
When Company A announces a proposed takeover of Company B, this creates a classic "game." Investors need to assess: will the takeover succeed? At what price?
According to QuantifiedStrategies, risk arbitrage is a strategy that analyses all players (buyers, sellers, regulators, shareholders) and predicts their actions. This is game theory in its purest form.
In options trading, the Prisoner's Dilemma concept is applied through strategies like straddles - where traders buy both call and put options at the same strike price, betting that the market will move significantly in one direction without needing to predict which direction.
The protective put strategy reflects the "Ultimatum Game" concept - how much are you willing to pay to protect your portfolio from losses?
Market makers use game theory every day. They need to set an optimal bid-ask spread - too wide will scare off investors, too narrow will reduce their profits.
This is a classic example of Nash Equilibrium - market makers seek a balance point where their spread is competitive enough to attract volume, yet wide enough to cover their risk.
The stock market as a whole is one massive confidence game. When the majority of investors are confident (bull), the market rises. When the majority are fearful (bear), the market falls.
From a game theory perspective, this resembles a coordination game - where all players benefit when they choose the same strategy. The problem is, nobody knows when the majority will change their minds.
One of the most important lessons from Axelrod's experiment is how emotions and psychology influence strategic decisions.
Strategies that tried to be "smarter" - those that attempted to exploit weaknesses, manipulate, or were overly complex - almost all lost in the long run. This aligns with what we see in trading:
Like Tit for Tat, successful investors tend to share the same traits:
The 2008 global financial crisis was a perfect example of the Prisoner's Dilemma on a massive scale. Banks had a choice: follow conservative lending practices (cooperate) or take excessive risks for short-term profits (defect).
Every bank chose to "defect" - offering high-risk loans because it was profitable in the short term. But when all banks did this, the financial system collapsed and everyone lost.
The tariff war between the United States and China can also be analysed through game theory. Both nations know that free trade (cooperation) benefits all parties. But each side has an incentive to impose tariffs (defect) to protect domestic industries.
The result? Both sides impose tariffs, and investors worldwide - including those on Bursa Malaysia - feel the impact.
When a stock on Bursa Malaysia suddenly surges, many retail investors rush to buy. This is an example of a "coordination game" - everyone trying to follow the same direction.
But from a game theory perspective, late entrants are actually playing a different game. They depend on others continuing to buy after them - an assumption that is often wrong.
Axelrod's experiment showed that winning strategies differ depending on the number of rounds. In a one-shot game, defecting is "rational." But in repeated games, cooperation is more profitable.
The stock market is a repeated game. You will continue investing for years. Traders who play as if every day is their last game tend to make overly aggressive and high-risk decisions.
Game theory teaches us that the outcome of our decisions depends on others' actions. Investors who focus solely on technical or fundamental analysis without considering what other investors might do are playing with incomplete information.
One reason Tit for Tat succeeded is because it was predictable. Opponents knew what would happen - if they cooperated, Tit for Tat would cooperate. This facilitated cooperation.
Investors who lack a clear trading plan - who change strategies every week - are actually making things harder for themselves. They are not sending consistent "signals" to the market.
When investors suffer major losses, many try to "get revenge" - doubling their position to recover losses. From a game theory perspective, this is like the "Always Defect" strategy that has been proven to fail in the long run.
Tit for Tat teaches us to retaliate when necessary but also to forgive. In trading, this means: cut losses when needed, but do not let emotions control your next decision.
Game theory is the study of how people make strategic decisions when their decisions influence and are influenced by the decisions of others. In the context of investing, it helps investors understand the interactions between buyers and sellers in the stock market.
Game theory is not a tool for precisely predicting stock prices. It is more of a thinking framework that helps investors understand market dynamics and make better decisions based on expectations of what other investors might do.
Tit for Tat is a game theory strategy where you start by cooperating, then mirror your opponent's previous action. In trading, this translates to: follow the market trend, respond to changes, and do not be too stubborn with any single position.
Nash Equilibrium in the stock market occurs when a stock price reaches a point where no investor has an incentive to change their strategy. This typically happens at strong support and resistance levels.
Yes. Beginners do not need to understand the complex mathematics behind game theory. Simply understanding the basic principles - always have a plan, cut losses quickly, do not try to "outsmart" the market, and think about what other investors might do - is sufficient.
Technical analysis focuses on price patterns and volume to predict future movements. Game theory focuses on strategic interactions between investors. Both can be used complementarily - technical analysis shows "what" is happening, game theory helps understand "why" it is happening.
Panic selling is a classic example of the Prisoner's Dilemma. Every "rational" investor wants to sell before prices fall further (defect). But when everyone sells simultaneously, prices drop even worse and everyone loses more than if they had stayed calm (cooperated).
No. Game theory can be applied across various fields including forex, crypto, property, business, and even everyday life. Its core principle - understanding how your decisions and others' decisions influence each other - is relevant in almost any situation involving strategic interaction.
Game theory teaches us something profoundly important - in long-term games, simple, honest, and consistent strategies often beat complex and manipulative ones. Axelrod's experiment proved that Tit for Tat - a four-line code strategy - could defeat hundreds of strategies designed by experts from around the world.
For investors and traders on Bursa Malaysia, this lesson is highly relevant. Do not try to be "too clever." Stick to a clear plan, cut losses quickly, return to your original strategy when conditions change, and always think about what other players might do.
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