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Understanding Causality: What Investors Often Get Wrong



As an investor, determining cause-and-effect relationships is crucial for making sound investment decisions. However, correctly identifying causality can be more difficult than it seems. There are some common ways that investors misunderstand or misattribute causality, which can lead to poor choices.




One of the biggest causality mistakes investors make is confusing correlation with causation. Just because two variables are correlated, or tend to move together, does not necessarily mean one is causing the other. For example, ice cream sales and drowning deaths are highly correlated because they both tend to rise in the summer. But higher ice cream sales are not causing more people to drown - the summer heat is a common cause behind both. As an investor, just because two economic or market factors appear correlated does not mean you have found a causal relationship to exploit.



Related to correlation and causation is the third variable problem. Investors sometimes conclude X is causing Y without realizing there is actually a third factor, Z, driving both X and Y. For example, you might observe that when interest rates fall, stock prices tend to rise and conclude lower rates are causing market gains. However, both could actually be reacting to expectations for economic growth. Knowing when an unseen third variable may be distorting a supposed causal link is difficult but important.


Reverse Causality


Another causality trap for investors is reverse causality, or switching cause-and-effect. A classic example is assuming that economic expansions cause bull markets. However, early bull markets often drive economic growth as the wealth effect of rising stocks boosts consumer and business spending. It's easy to flip sequences around, so carefully consider the timeline when asserting a causal claim.


Overlooking Context


Investors can make the mistake of declaring causality without considering context. For example, tight monetary policy from a central bank usually dampens inflation. So you might expect the same result in a given country based on past observations. However, in a new economic environment or under a different policy regime, those prior causal links can break down. The context surrounding statistical relationships matters greatly.


Failing to Establish Temporal Precedence


Determining which variable occurred first is a key aspect of proving causality. However, investors may simply look at patterns in the data without verifying the timing. For example, you may believe that rising inflation causes the Federal Reserve to hike interest rates after seeing this relationship play out. Yet during some periods, the Fed started hiking rates before inflation picked up, indicating interest rate changes were actually driving inflation rather than responding to it. Carefully verifying whether alleged causes actually precede effects is vital work for establishing causality.


Extrapolating Too Far


It's often said that past performance does not guarantee future results. This causality trap bites investors who make predictions by extrapolating causal relationships beyond reasonable bounds. For example, the tendency for stocks to rebound after mid-term election years may lead investors to expect strong returns after every midterm. However, extending such causal links too far into the future often leads to disappointments. Causal relationships in markets have limits and parameters that must be acknowledged.


Ignoring Bidirectional Causality


In complex systems like the economy and financial markets, causality often runs two ways rather than one. However, investors frequently focus on just one direction. For instance, the prevailing assumption may be that consumer sentiment drives market returns, so sentiment indexes get all the attention. Yet when stocks are rising, sentiment typically improves too. Failing to account for feedback loops and bidirectional flows of cause-and-effect can throw off analysis.


In investing, getting causality right matters. Billions of dollars ultimately hang on properly identifying what causes what in financial and economic trends. While humans may never perceive causality perfectly, avoiding these common errors and fallacies goes a long way toward making sound, evidence-based investment decisions. Avoiding these causality pitfalls takes vigilance and not taking correlations or historical tendencies at face value. But critical thinking around the true drivers of economic and financial trends can pay off considerably for investors. Applying rigorous logic around cause-and-effect is key to deploying capital wisely based on facts rather than false assumptions.

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