Decision Fatigue in Investing: How Too Much Choice Leads to Poor Returns

We’ve all been there. Standing in the supermarket aisle, trying to make sense of the vast number of products available to us in every single category. Does a cheaper toothpaste mean it’s less effective? We think through the benefits of saving money by buying products on sale versus a vast number of other micro-decisions that collectively drive our final choice.

It’s exhausting. And it’s exactly the same in the investment world.

This is an environment defined by overwhelming abundance. According to the ASX, the number of ETFs listed locally ballooned from fewer than 50 in 2010 to more than 400 by 2025, while global ETF assets have surpassed US$19.5 trillion.

On the surface, this proliferation should empower investors. In practice, it often paralyses them.

Decision Fatigue is a Real Thing

The concept of decision fatigue, first explored in the behavioural sciences by Roy Baumeister, describes the deteriorating quality of decisions after a prolonged period of choice.

The paradox is that more choice should improve outcomes by enabling precision. Instead, it often leads to inertia, suboptimal allocation, and performance drag.

Sadly, decision fatigue has become a significant challenge for most investors.

The evidence is unequivocal.

Vanguard’s study of US retirement plans found that participation rates declined as the number of available funds increased. When plans offered two funds, participation exceeded 75%. When the menu expanded to more than 50 options, participation fell towards 60%. More strikingly, investors allocated disproportionately to familiar or recently visible options rather than optimally diversified portfolios.

The problem is that this type of decision fatigue directly translates into lower long-term returns through poor diversification and mistimed entry points.

The same dynamic is observable in ETF flows.

Morningstar data shows that global capital tends to concentrate in a narrow subset of products despite an expanding universe.

It’s similar in the Australian market. Broad market ETFs such as those tracking the S&P/ASX 200 continue to dominate inflows, while more specialised exposures tend to experience episodic surges driven by narratives rather than sustained allocation decisions.

This clustering confirms that investors, when faced with excessive choice, revert to heuristics such as familiarity and recent performance rather than systematic portfolio construction.

It Takes a Toll

The cost of decision fatigue is high.

Decision fatigue reduces the cognitive capacity required for disciplined, long-term thinking. It stops investors from seeing the wood for the trees. In the end, they often make decisions with a disempowered mindset aimed at getting the job done.

It’s easy to understand why.

The domestic ETF market now spans broad equity exposures, sector-specific strategies, thematic funds focused on areas such as AI and the energy transition, and increasingly sophisticated fixed income products.

The psychological response to so much complexity often manifests as either over-diversification or complete avoidance.

Over-diversification, sometimes referred to as ‘diworsification’, occurs when investors hold an excessive number of overlapping funds in an attempt to cover all possibilities.

However, there’s plenty of research proving that beyond a certain point, additional diversification provides diminishing benefits while increasing transaction costs and diluting conviction.

Conversely, avoidance leads to under-investment or excessive cash holdings.

Technology has intensified the problem. Digital platforms provide real-time data, performance rankings, and comparison tools.

While these features are designed to inform, they also create an environment of constant evaluation.

Each additional metric introduces another decision variable.

Behavioural finance research from Harvard Business School has demonstrated that when individuals are presented with too many attributes to evaluate, they are more likely to rely on simplified decision rules or defer decisions altogether.

In investing, this can mean chasing top-performing funds or remaining uninvested during periods of uncertainty, both of which can be devastating to portfolio returns.

Volatility Makes the Problem Worse

The interaction between decision fatigue and market volatility is particularly damaging.

During periods of heightened uncertainty, such as the pandemic-driven selloff of 2020, investors need to process rapidly changing information while concurrently managing their emotional stress.

All the while, they need to be aware that their instinct to sell during bouts of weakness will almost always be detrimental to their performance.

Fidelity research shows that investors who avoid portfolio changes during volatile periods achieved better outcomes than those who trade frequently.

The implication is at odds with the industry’s direction of travel: the ability to reduce decision frequency, rather than increase it, is a powerful source of competitive advantage.

And vice versa: technology that provides you with unguided access to a wider universe of products is likely to hinder your ability to make good decisions.

Key Takeaways

There are a few important takeaways for investors:

- Simplifying the decision framework can materially improve outcomes.

This means reducing unnecessary complexity. Investors who define a clear asset allocation, grounded in long-term objectives rather than short-term narratives, are less susceptible to the cognitive overload that drives poor decisions.

- The role of investment platforms is critical.

Tools that enable comparison based on a limited set of meaningful metrics, such as total return, volatility, and income distribution, are more effective than those presenting dozens of variables simultaneously.

- The most effective response is a disciplined process that limits the number of decisions required over time.

This includes committing to a small number of well-understood exposures, maintaining alignment with your asset allocation plan, and resisting the impulse to react to short-term performance signals.

One way to ensure your process remains on track is to automatically invest into a shortlist of managed funds and ETFs each and every month. The key is to take as many decisions out of your process as possible so your portfolio can compound over the long term without being derailed by decision fatigue.

Keep it Simple

In a world of abundant choice, the marginal benefit of additional investment options is outweighed by the cognitive cost they impose. The path to better returns lies not in embracing every available opportunity, but in deliberately narrowing the field of decisions.

Disclaimer: This article is prepared by Simon Turner. It is for educational purposes only. While all reasonable care has been taken by the author in the preparation of this information, the author and InvestmentMarkets (Aust) Pty. Ltd. as publisher take no responsibility for any actions taken based on information contained herein or for any errors or omissions within it. Interested parties should seek independent professional advice prior to acting on any information presented. Please note past performance is not a reliable indicator of future performance.