How does bias affect investors and cost you money?

In the investing world, biases can significantly impact the decision-making process and, ultimately, the performance of portfolios. These biases, often rooted in psychological traits, can lead to irrational thinking and suboptimal investment choices. The effects of these biases on investors are worth examining to understand the potential pitfalls better and improve investment strategies.

Various biases influence investors, such as overconfidence, herd behavior, and loss aversion.

Overconfidence can lead investors to believe that their knowledge or ability is superior to that of others, causing them to take on excessive risks or trade too frequently.

Herd behavior occurs when investors follow the actions of others rather than making their own independent decisions based on financial data.

Loss aversion is another common bias, where the fear of losing money causes investors to act irrationally, sometimes resulting in prematurely holding onto poorly performing investments or selling good investments.

By understanding and recognizing these biases, investors can work towards more objective decision-making and better investment outcomes.

How Does Bias Affect Investors? Understanding Bias in Investing

Bias in investing refers to the irrational assumptions or beliefs that can impact an investor’s ability to make objective decisions based on facts and evidence. It is essential to recognize and manage these biases to improve investment outcomes.

Cognitive Bias

Cognitive biases are systematic errors in thinking that can influence how investors process and evaluate information. These biases can lead to flawed decision-making and negatively impact an investor’s portfolio. Some common cognitive biases include:

  • Confirmation bias: The tendency to search for, interpret, and remember information in a way that confirms one’s preconceived beliefs or hypotheses while giving less importance to contradictory information. This can lead to overconfidence and ignoring warning signs in the market.
  • Recency bias: The inclination to focus on the most recent events or data, which may not represent the longer-term trends. This can cause investors to make impulsive decisions based on short-term market fluctuations.
  • Anchoring bias: The tendency to rely too heavily on the first piece of information encountered when making decisions. For example, an investor may anchor their expectations of a stock’s performance on its initial purchase price, making it difficult to sell at a loss when necessary.

Emotional Bias

Emotional biases are rooted in feelings and instincts rather than objective analysis. These biases can cause investors to make irrational decisions driven by emotions, such as fear or greed. Some common emotional biases include:

  • Loss aversion: The tendency to feel the pain of a loss more intensely than the pleasure of a gain. This can lead to investors holding onto losing investments for too long, hoping they will rebound, or selling winners too soon to lock in profits.
  • Overconfidence: The belief that one’s skills or intuition are superior to others or the market in general. Overconfidence can lead to excessive risk-taking or ignoring evidence that challenges one’s beliefs.
  • Herd mentality: The tendency to follow the actions or beliefs of a larger group, even when it may not be rational or in one’s best interest. An example of herd mentality is investors flocking to a popular stock, driving up its price beyond its intrinsic value.

By being aware of these cognitive and emotional biases, investors can work towards making more informed and rational decisions that better align with their long-term investment goals.

How Does Bias Affect Investors? Common Biases

How does overconfidence bias affect investors

Overconfidence Can Cost You

Investors encounter numerous psychological biases that may influence their decision-making process. This section will discuss five common biases and their effects on investors’ behavior.

Overconfidence Bias

Overconfidence bias occurs when investors believe their knowledge or abilities are superior to others.

This may lead them to make riskier decisions, as they assume they can accurately predict market movements. Overconfidence can also result in excessive trading, negatively affecting returns due to higher transaction costs and taxes.

Confirmation Bias

Confirmation bias is the tendency to favor information that confirms existing beliefs and disregard information that contradicts those beliefs.

This bias can result in investors ignoring vital warning signs or holding onto underperforming investments because they focus solely on the evidence that supports their initial decisions.

Herd Mentality

Herd mentality refers to the inclination of investors to follow the actions and trends of the market rather than relying on their independent analysis.

This can contribute to speculative bubbles and crashes, as investors might base their decisions more on the behavior of others than on actual economic fundamentals.

An index (Herd Behavior Index) was created for financial professionals to use, either trading with the herd or against the herd. Here is more about the research paper and the index development if you want to learn more.

Dhaene, Jan & Linders, Daniël & Schoutens, Wim & Vyncke, David. (2012).

The Herd Behavior Index: A New Measure for the Implied Degree of Co-Movement in Stock Markets.

Insurance Mathematics and Economics. 50. 357-370. 10.2139/ssrn.1926191. We introduce a new and easy-to-calculate measure for the expected degree of herd behavior or co-movement between stock prices.

This forward looking measure is model-independent and based on observed option data. It is baptized the Herd Behavior Index (HIX)

The degree of co-movement in a stock market can be determined by comparing the observed market situation with the extreme (theoretical) situation under which the whole system is driven by a single factor.

The HIX is then defined as the ratio of an option-based estimate of the risk-neutral variance of the market index and an option-based estimate of the corresponding variance in case of the extreme single factor market situation.

The HIX can be determined for any market index provided an appropriate series of vanilla options is traded on this index as well as on its components. As an illustration, we determine historical values of the 30-days HIX for the Dow Jones Industrial Average, covering the period January 2003 to October 2009.

Loss Aversion

Loss aversion is the tendency for investors to feel the pain of losses more acutely than the pleasure of gains.

This can lead to holding on to losing investments in the hope that they will rebound while selling winning investments too soon to lock in profits.

Loss aversion can hamper investors’ long-term returns, as they may miss opportunities for growth in favor of avoiding short-term losses.

Anchoring Bias

Anchoring bias is the process of relying too heavily on an initial piece of information, typically the purchase price of an investment, when making future decisions.

This can lead to poor judgment in evaluating an asset’s current or future value. For example, an investor might refuse to sell an underperforming stock because its price has fallen below the initial purchase price, even if it no longer represents a good investment.

How Does Bias Affect Investors? Impact on Investment Decisions

Biases can significantly affect investor behavior and decision-making processes. In this section, we’ll explore the effects of these biases on different aspects of investment, including poor diversification, increased risk-taking, missed opportunities, and reduced investment performance.

Poor Diversification

Investors who fall prey to biases tend to make poor diversification decisions. For example, they may exhibit home bias, or the tendency to invest primarily in domestic assets, leading to less diversified portfolios.

This may expose them to increased risk due to the concentration of their investments in a single market or sector. You see this with smaller real estate investors that only buy property in their local market. A natural disaster can wipe them out – they have no geographical diversification.

Very risky.

Increased Risk-Taking

Biases can lead to an increase in risk-taking among investors.

For instance, the overconfidence bias can make investors overestimate their knowledge and ability to make accurate predictions, resulting in a higher likelihood of taking excessive risks. There is a reason why 97% of day traders lose money.

Click here to learn more

Chague, Fernando and De-Losso, Rodrigo and Giovannetti, Bruno, Day Trading for a Living? (June 11, 2020). Available at SSRN: or

We show that it is virtually impossible for individuals to day trade for a living, contrary to what course providers claim. We observe all individuals who began to day trade between 2013 and 2015 in the Brazilian equity futures market, the third in terms of volume in the world.

We find that 97% of all individuals who persisted for more than 300 days lost money. Only 1.1% earned more than the Brazilian minimum wage, and only 0.5% earned more than the initial salary of a bank teller — all with great risk.

Similarly, herd behavior, where investors follow the actions of others rather than their analysis, can lead to irrational risk-taking.

Missed Opportunities

Several cognitive biases can result in investors missing out on lucrative investment opportunities.

One such bias is present bias, which can cause investors to favor short-term gains over long-term benefits, leading them to overlook opportunities that might have been more rewarding over time.

Additionally, anchoring bias can make investors reluctant to invest in assets that have increased in price, believing that they have missed the best opportunity to purchase them, which may not be accurate.

Reduced Investment Performance

Ultimately, the impact of these biases can lead to reduced investment performance.

Poor diversification, increased risk-taking, and missed opportunities may all contribute to suboptimal investment returns. By being aware of these biases and actively working to mitigate their influence, investors can make more informed decisions and improve their overall investment success.

Overcoming Bias in Investing

Self-Awareness and Education

One of the first steps to overcoming bias in investing is becoming self-aware and understanding the common biases that can influence decision-making.

By educating themselves on these biases, investors can recognize them within their thinking and adopt strategies to mitigate their impact.

For example, understanding herd behavior, loss aversion, and mental accounting concepts can help improve decision-making and lead to better investment outcomes.

Financial Planning and Objectives

Having clear financial goals and a well-thought-out plan can reduce the influence of biases on investment decisions.

By establishing an investment strategy that aligns with personal objectives, investors can avoid making decisions based solely on short-term market movements or popular trends.

Focusing on long-term investing success and adhering to a plan can help investors maintain a rational perspective and reduce the impact of emotional biases.

Working with Financial Professionals

Another strategy to overcome bias is to work with financial professionals, such as financial advisors or portfolio managers.

These professionals can offer objective advice and guidance, helping investors avoid biased thinking and make informed decisions.

Additionally, their experience and market knowledge can provide valuable insights that can aid investors in achieving their investment goals.

Utilizing Investment Tools and Analytical Solutions

Investors can also leverage various investment tools and analytical solutions to help mitigate the impact of biases in their decision-making processes.

For example, utilizing risk assessment tools can help investors objectively evaluate the potential risks of their investment choices.

Developing a structured approach to analyzing and selecting investments can also help reduce the influence of biases in decision-making.

How Does Bias Affect Investors? Final Thoughts

How does bias affect investors?


Biases shape investor decisions and impact their financial outcomes.

Seeing and overcoming bias in yourself is very difficult, but it can be done. Understand what these biases are and work to both see them in your behavior and then overcome them.

Several different new technologies can help mitigate biases, such as quantitative investing, robo-advisors, and AI investing systems. I leverage all of these in my investing activities but still battle biases.

I try to learn and get better a little bit every day.

Good luck!