Why Stock Market Explanations Are Often Wrong

A behavioural finance perspective on why convincing stories can mislead investors—and why accepting uncertainty may lead to better decisions.

A stock falls by 10% shortly after the market opens.

Within minutes, the explanations begin appearing:

“Investors are worried about slowing sales.”

“The company is facing supply-chain problems.”

“The market has lost confidence in management.”

“The stock had simply become too expensive.”

Each explanation sounds logical. Yet different commentators may offer completely different reasons for the same price movement.

So, which explanation is correct?

The honest answer is often: we do not really know.

A stock price reflects the actions of thousands—or even millions—of market participants. They may be buying or selling for completely different reasons.

Nevertheless, our minds are uncomfortable with uncertainty. We would rather have a simple explanation than accept that the market is complicated, unpredictable and sometimes impossible to understand.

Most people assume that every significant stock market movement must have a clear cause.

If a stock falls after the company reports weaker sales, the conclusion seems obvious:

“The stock fell because sales declined.”

If a company announces record profits and its share price rises:

“The stock rose because earnings were strong.”

Financial news reinforces this belief. Headlines frequently tell us that stocks rose “because of” an economic announcement or fell “due to” investors’ concerns.

These explanations give us the comforting impression that the market is understandable. If we can explain yesterday’s movement, perhaps we can predict tomorrow’s.

Unfortunately, it is rarely that simple.

In behavioural finance, this tendency is known as the narrative fallacy.

The narrative fallacy describes our preference for a neat and convincing story over a complicated reality. Once we know the outcome, we connect selected facts in a way that makes the outcome appear logical and predictable.

This is partly caused by hindsight bias. After an event has happened, the warning signs seem more obvious than they really were beforehand.

It is also connected to overconfidence. We may believe that because an explanation sounds reasonable, it must be correct.

However, a plausible explanation is not the same as a proven cause.

A stock can move because of many interacting factors:

• Changes in revenue or profits
• Management’s future guidance
• Interest-rate expectations
• Institutional portfolio rebalancing
• Forced selling or liquidity needs
• Options-related hedging
• Algorithmic trading
• Industry developments
• Investor sentiment
• Fear, greed and speculation

Some of these factors may not be visible to the public at all.

When we reduce a stock’s movement to one simple reason, we may ignore the messy combination of expectations, incentives and market mechanics operating beneath the surface.

Throughout my investing journey, I have noticed how quickly people search for explanations whenever a stock rises or falls sharply.

If a company encounters a supply disruption and its share price falls, people may immediately conclude that the supply problem caused the decline.

That may be true—but it may not be the full story or even the main reason.

Perhaps the company’s sales were already slowing. Perhaps management lowered its earnings forecast. Perhaps profit margins disappointed investors. Perhaps a large fund was reducing its position. Perhaps expectations had simply become too optimistic.

All these factors could be affecting the share price simultaneously.

More importantly, markets do not react only to what happened. They react to the difference between what happened and what investors had already expected.

A company can report falling sales and still see its share price rise if the market expected an even worse result. Conversely, a company can announce record profits and watch its share price fall if investors had expected stronger numbers.

This is why knowing the news does not necessarily tell us why the price moved.

From The Value Steward perspective, the lesson is not that we should ignore information. It is that we should be more humble about how confidently we interpret it.

Sometimes, saying “I don’t know” reflects greater wisdom than confidently repeating an attractive story.

Before acting on a market explanation, separate it into three layers.

1. What Happened?

Begin with facts that can be observed and verified.

For example:

• The company’s quarterly revenue declined by 10%.
• Management lowered its earnings guidance.
• A factory suspended production.
• The stock price fell by 8%.

These statements describe events without claiming why the market reacted.

2. What Might It Mean?

Next, consider reasonable interpretations.

For example:

• The company may be losing market share.
• The supply disruption may affect future profits.
• Management’s assumptions may have been too optimistic.
• The business may be facing a temporary setback.

These interpretations may help us analyse the investment, but they still require judgment. They should not be treated as established facts.

3. What Story Am I Telling Myself?

Finally, identify the story you have constructed around the events.

For example:

• “Investors sold because they were worried about the supply disruption.”
• “The market has finally realised that the CEO is overrated.”
• “The stock will recover once sentiment improves.”
• “This company always overcomes its problems.”

These stories may eventually prove correct. But they may also be incomplete, overly confident or entirely wrong.

This framework creates a margin of safety in our thinking.

In value investing, a margin of safety protects us when our estimates are inaccurate. In decision-making, intellectual humility performs a similar function. It leaves room for the possibility that our explanation is incomplete and that the future may unfold differently from what we expect.

Imagine that a technology company reports weaker quarterly sales and its stock falls by 12%.

One commentator blames weak consumer demand.

Another says investors are worried about a new competitor.

A third argues that higher interest rates have made growth stocks less attractive.

All three explanations may sound believable. All three may even contain some truth.

But the people who sold the shares may have acted for very different reasons.

A fund manager might have been rebalancing a portfolio. Another investor might have needed cash. A trading algorithm could have reacted automatically to a disappointing figure. Some shareholders might have panicked after seeing the initial decline.

We can verify that sales weakened and the stock fell.

What we cannot easily prove is that every seller—or even most sellers—acted because of the same piece of information.

It is similar to seeing a crowded restaurant suddenly become empty and concluding that the food must be bad. Perhaps several customers finished eating at the same time. Perhaps a large group had another appointment. Perhaps there was a problem with the air-conditioning.

The most visible explanation is not necessarily the most important one.

This uncertainty is one reason I prefer investing mainly in broad index exchange-traded funds, or ETFs.

Instead of depending heavily on my ability to correctly interpret every development affecting an individual company, I can own a diversified group of businesses. Some will struggle, while others will grow and become more important within the index.

This does not mean index ETFs grow consistently every year. They can fall sharply, remain below previous highs for long periods and deliver disappointing returns. Future growth is never guaranteed.

However, diversification reduces the consequences of being wrong about one company. It allows me to participate in broad economic growth without needing every market explanation—or every stock selection—to be correct.

The next time a stock or market index moves sharply, try the following:

Pause before accepting the headline

Treat the explanation as one possible interpretation, not an established fact.

Separate facts from opinions

Write down what actually happened, followed by what you think it means. Do not mix the two.

Ask what the market expected

A result can be objectively good but disappointing relative to expectations. Similarly, bad news can produce a positive market reaction if investors feared something worse.

Consider alternative explanations

Ask yourself:

• What else could have contributed to this movement?
• Am I focusing on this explanation only because it is the most visible?
• Would I believe the same story if the price had moved in the opposite direction?

Focus on long-term business fundamentals

Instead of trying to explain every daily price movement, examine whether the company’s long-term earning power, competitive position and financial strength have materially changed.

Use diversification as protection against uncertainty

If you cannot—or do not want to—analyse individual companies deeply, a diversified portfolio of low-cost index ETFs may be more suitable than relying on a few compelling stock stories.

Build a process that does not require perfect explanations

Decide in advance how you will invest, diversify and respond to volatility. A sound system helps prevent every headline from becoming a reason to change your portfolio.

A good story can make the market feel understandable, but confidence is not evidence.

We may never know the exact reason why a stock rose or fell—and we do not need to. The goal is not to explain every market movement perfectly. It is to build an investment process that remains sensible even when our explanations are incomplete or wrong.

Have you ever seen a stock move in the opposite direction from what the news appeared to suggest? What did that experience teach you about market explanations?

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