Should I Invest in What I Love? Product Affection vs Investment Logic

Personal product preferences are often the worst possible guide to investment decisions.

I remember when my family first got a GoPro. Revolutionary technology, stunning footage – everyone wanted one. Naturally, I thought: "This company is going places. Maybe I should buy shares." It's a seductive logic: if I love the product, surely others will too. A decade later, I'm thankful I didn't act on that impulse.

This instinct to invest in what we know and love feels intuitive. We use the products, we understand them, we see their value. But this emotional connection – what behavioural economists call "familiarity bias" – is precisely what makes it dangerous.

Back in 2014, GoPro went public and quickly hit a market capitalization of $10 billion with virtually no competition. Today? The stock trades around $1.87 per share – down 98% from its peak, with over $9.7 billion in market value lost.

What went wrong?

Smartphones killed the action camera star. Modern phones became waterproof, gained multiple lenses, and developed image stabilisation that rivals dedicated cameras. GoPro thought they were competing against other action cameras when they were actually competing against the most successful consumer device in history.

But here's the deeper lesson: loving a product tells you nothing about the company's competitive position or long-term viability. A great product is necessary but far from sufficient for investment success. In GoPro's case, every smartphone manufacturer became their competitor, each with deeper pockets and products consumers were already buying.

The Pattern Repeats Closer to Home

This isn't just an overseas story. Take My Food Bag – during COVID lockdowns, it seemed genius. The company went public in March 2021 at $1.85 per share, raising $342 million. Customers loved the service and bought shares. Many retail investors had enjoyed watching co-founder Nadia Lim cook on TV for years – hardly grounds for a wise investment decision. The result? Shares now trade around 25 cents – an 86% decline. As one fund manager noted, "It was a classic private equity exit, which has seen a lot of retail investors lose out."[1]

The timing seemed perfect. Lockdowns had created new habits. People were cooking at home more. The convenience model made sense. But investors failed to ask: what happens when lockdowns end? Is this a permanent behaviour shift or a temporary adaptation? How defensible is the business model? These are the uncomfortable questions that emotional attachment prevents us from asking.

As one fund manager noted, "It was a classic private equity exit, which has seen a lot of retail investors lose out."

Then there's Ryman Healthcare, beloved by many Kiwi families for good reason. My own family experienced the amazing care and kindness shown towards my late father during his time in the dementia care unit at Ryman in Havelock North. The quality of their villages is genuinely impressive. Yet despite these strengths, the stock hit $10.87 in December 2019 and now trades around $2.87 – down 74%. The investment thesis crumbled under construction delays and regulatory challenges, demonstrating that exceptional service doesn't automatically translate into strong investment returns.

This one hits close to home because the service was excellent. But gratitude and investment logic operate in different domains. A company can deliver outstanding customer experiences while simultaneously facing operational headwinds that undermine shareholder returns.

These three examples share a common thread: product or service quality created an emotional connection that clouded rational investment analysis.

The Evidence Against Emotional Investing

Behavioural finance research identifies "familiarity bias" as a major driver of poor investment decisions, where investors favour what they know rather than what performs best.[2] This bias is particularly pronounced amongst long-term investors who believe they're securing against volatility when they're actually concentrating risk.

The evidence against stock picking is overwhelming:

An Arizona State University study by Professor Hendrik Bessembinder examining over 28,000 stocks from 1926 to 2024 found that just 4% of firms created all net wealth in the U.S. stock market. The remaining 96% collectively matched Treasury bills over their lifetimes, and the majority of individual stocks actually reduced shareholder wealth compared to holding cash.[3]

Think about that. If you picked a stock at random, you'd have better than even odds of underperforming cash. The market's impressive returns come from a tiny fraction of companies – and identifying them in advance is nearly impossible.

Professional fund managers fare no better. S&P Dow Jones Indices' SPIVA Scorecard shows that after 10 years, approximately 85% of large-cap funds underperform the S&P 500, and after 15 years, around 90% trail the index.[4] Even Warren Buffett admits: "In 58 years of Berkshire management, most of my capital-allocation decisions have been no better than so-so."[5]

These aren't amateur investors. These are professionals with research teams, Bloomberg terminals, insider access, and decades of experience. If they can't beat a simple index fund, what makes individual investors think they can, especially when driven by product affection rather than analysis?

The Smart Money Questions

Instead of asking "Do I love this product?", evidence-based investors ask: How big is the addressable market? What prevents competitors from copying this? How strong are the financials? Is the company innovating fast enough? What could make this product obsolete?

These questions are deliberately uncomfortable because they force you to look beyond your emotional attachment. They require research, analysis, and a willingness to acknowledge uncertainty. Most importantly, they shift the focus from "I like this" to "can this company maintain a durable competitive advantage?"

The answers usually point to the same solution: diversification. Diversified index funds consistently outperform stock picking over the long term, providing market-matching returns while reducing the risk of catastrophic losses from individual stock failures.[6]

Diversification isn't glamorous. There's no story to tell at dinner parties about your clever stock pick. But it's precisely this lack of excitement that makes it effective. By owning the entire market, you guarantee you'll own the 4% of companies that generate all the wealth creation, without needing to predict which ones they'll be.

As a fee-only adviser working with evidence-based strategies, the real value isn't in chasing hot stocks or validating product obsessions. It's in building a robust financial plan grounded in decades of research, then maintaining discipline through market noise and emotional temptation.

This discipline is harder than it sounds. When GoPro was soaring, when My Food Bag was listing during lockdowns, when you're genuinely grateful for care received – the emotional pull to invest is powerful. It feels like you have special insight. You don't. You have an emotional connection clouding your judgment.

The most valuable thing a good adviser provides isn't stock tips or market predictions. It's the voice of reason when your emotions are screaming at you to invest in what you love. It's the person who asks the uncomfortable questions: "Have you analyzed the competitive landscape? What's your exit strategy? How does this fit your overall plan?" These questions aren't exciting, but they're essential.

Seek wise counsel, commit to a plan that aligns with your goals, and redirect that energy from stock-picking to living your life. Enjoy the products you love. Be grateful for excellent service. Just don't confuse these feelings with investment insight.

Your future self will thank you for choosing evidence over emotion.

Nick Stewart

(Ngāi Tahu, Ngāti Huirapa, Ngāti Māmoe, Ngāti Waitaha)

Financial Adviser and CEO at Stewart Group

• Stewart Group is a Hawke's Bay and Wellington based CEFEX & BCorp certified financial planning and advisory firm providing personal fiduciary services, Wealth Management, Risk Insurance & KiwiSaver scheme solutions.

• The information provided, or any opinions expressed in this article, are of a general nature only and should not be construed or relied on as a recommendation to invest in a financial product or class of financial products. You should seek financial advice specific to your circumstances from a Financial Adviser before making any financial decisions. A disclosure statement can be obtained free of charge by calling 0800 878 961 or visit our website, www.stewartgroup.co.nz

• Article no. 437

---

References

1. My Food Bag Group Limited. (2024-2025). Financial Results and Market Updates. NZX Announcements. Retrieved from https://investors.myfoodbag.co.nz/

   • Devon Funds Management. (2025). "My Food Bag Investment Analysis." RNZ Business Interview, May 22, 2025.

2. Huberman, G. (2001). Familiarity breeds investment. Review of Financial Studies, 14(3), 659–680. https://doi.org/10.1093/rfs/14.3.659

   • Chew, S.H., Li, K.K., & Sagi, J. (2023). Home bias explained by familiarity, not ambiguity. Social Science Research Network. https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3870716

   • De Vries, A., Erasmus, P.D., & Gerber, C. (2017). The familiar versus the unfamiliar: Familiarity bias amongst individual investors. Investment Analysts Journal, 46(1), 24-39.

3. Bessembinder, H. (2024). Shareholder wealth enhancement, 1926 to 2022 (Updated through 2024). Arizona State University, W.P. Carey School of Business. Retrieved from https://wpcarey.asu.edu/department-finance/faculty-research/do-stocks-outperform-treasury-bills

   • Bessembinder, H. (2018). Do stocks outperform Treasury bills? Journal of Financial Economics, 129(3), 440-457.

4. S&P Dow Jones Indices. (2024). SPIVA U.S. Scorecard Year-End 2024. Retrieved from https://www.spglobal.com/spdji/en/documents/spiva/spiva-us-year-end-2024.pdf

5. Berkshire Hathaway Inc. (2022). Letter to Shareholders. Annual Report 2022.

6. Malkiel, B.G. (2019). A random walk down Wall Street: The time-tested strategy for successful investing (12th ed.). W.W. Norton & Company.

   • Bogle, J.C. (2017). The little book of common sense investing: The only way to guarantee your fair share of stock market returns (10th anniversary ed.). John Wiley & Sons.

   • Fama, E.F., & French, K.R. (2010). Luck versus skill in the cross-section of mutual fund returns. The Journal of Finance, 65(5), 1915-1947.

Markets, Science, & the Chicago Legacy: Why Evidence Matters More Than Ever

Standing outside the University of Chicago Booth School of Business recently, I was struck by how this building represents something far more valuable than bricks and mortar.

The building bears the name of David Booth, founder of Dimensional Fund Advisors (DFA), whose $300 million donation in 2008 recognised the profound influence this institution has had on how we understand investing. It was the largest gift to any business school in history at the time—and for good reason. The University of Chicago has produced 97 Nobel Prize laureates, making it one of the world’s great centres of economic thought.

I’ve just returned from the United States, where I attended a conference and met with some of the most innovative wealth management firms operating today. What struck me most wasn’t the technology or the marketing—it was the unwavering commitment to letting science, not emotion, drive investment decisions.

The Chicago Revolution

The University of Chicago fundamentally changed how we understand markets. In the 1960s and 70s, Eugene Fama developed the Efficient Market Hypothesis, which challenged the prevailing wisdom that active stock pickers could consistently beat the market. His research, along with work by Harry Markowitz on portfolio theory and Merton Miller on corporate finance, created a scientific framework for understanding how markets actually work rather than how we wish they would work.

 These weren’t armchair theories. They were rigorously tested hypotheses backed by decades of data. Fama won the Nobel Prize in 2013.[1] More recently, Douglas Diamond, who serves as a director at DFA, won the Nobel Prize in 2022 for his groundbreaking research on banks and financial crises.[2] The message is clear: markets are remarkably efficient at incorporating information into prices, making it extraordinarily difficult for active managers to consistently outperform after fees.

From Theory to Practice

This is where David Booth’s story becomes fascinating. After studying under these pioneers at Chicago, he co-founded DFA in 1981 with a radical idea: academic research should drive investment strategy. Rather than trying to pick winners or time markets, DFA built portfolios that captured the dimensions of return that academic research had identified—company size, relative price, and profitability.

The firm’s commitment to its academic foundation remains extraordinary. Eugene Fama himself serves as a director and consultant to DFA, alongside Nobel laureate Douglas Diamond and numerous other distinguished academics.[3] This isn’t window dressing—these researchers actively shape the firm’s investment approach. Today, DFA manages over $850 billion globally and works exclusively with around 1,800 financial advisers and institutions worldwide who share their evidence-based philosophy.[4]

We’ve been fortunate to be part of that community since 2003. Over more than two decades, I’ve had the privilege of meeting David Booth himself, along with many of DFA’s esteemed researchers and team members. These aren’t just business relationships—they’re ongoing dialogues about how markets work and how we can best serve our clients.

But philosophy alone doesn’t pay the bills. The real work happens in translating these academic insights into portfolios that work for real New Zealanders with real goals. Our investment committee builds portfolios that harness these evidence-based principles while respecting each client’s individual circumstances. For some, that means incorporating ESG considerations—ensuring investments align with values without sacrificing returns. For others, it’s about smart tax planning, understanding how PIE funds, FIF rules, and portfolio location decisions can significantly impact after-tax wealth over time. The science tells us what works in markets; our job is to implement it in a way that works for you.

The Emotional Trap

During my US trip, I sat through presentations from wealth management firms managing billions in client assets. A common theme emerged: the biggest threat to investor success isn’t market crashes or economic recessions—it’s investor behaviour itself.

We’re hardwired for emotional responses that work against us in financial markets. We panic when markets fall and become euphoric when they rise. We chase last year’s winners and abandon sound strategies at precisely the wrong moment. We believe we can spot the next big thing, despite overwhelming evidence that even professionals cannot consistently do so.

The firms I met with have built their practices around protecting clients from themselves. They use science-based portfolio construction, maintain discipline during volatility, and focus on what investors can control: costs, diversification, tax efficiency, and most importantly, behaviour.

The New Zealand Reality

Here’s something I hear often: “But surely New Zealand is different?”

It’s not. Market principles are universal. New Zealand shares trade on the same fundamental dynamics as shares in New York, London, or Tokyo. The temptation to believe “it’s different here” often leads to home bias and concentrated portfolios that increase risk without increasing expected returns.

The evidence is unequivocal, regardless of geography. Studies consistently show that the average investor significantly underperforms the very funds they invest in, purely due to poor timing decisions. Research from Morningstar found that investors typically lag their own investments by 1-2% annually simply by buying high and selling low.[5] This behaviour penalty applies equally to investors in Auckland as it does in Austin.

Think about that: a 1-2% annual drag from poor timing decisions alone. Over a 30-year investment horizon, that’s the difference between retiring comfortably and struggling to make ends meet. And it has nothing to do with market returns or fund performance—it’s entirely self-inflicted through emotional decision-making.

What This Means for You

As your advisers, our role isn’t to predict the future or pick winning stocks. It’s to help you stay invested in sensibly constructed, evidence-based portfolios through all market conditions. The science tells us that markets reward patient investors who remain diversified and resist the urge to react to short-term noise.

This matters now more than ever. With 24/7 news cycles, social media investment “gurus,” and the constant temptation to react to market movements, maintaining discipline has never been harder—or more important.

When markets inevitably experience volatility (and they will), remember this: every market downturn in history has eventually been followed by recovery. The investors who stayed disciplined and remained invested captured those recoveries. Those who sold in panic and tried to time their re-entry typically bought back in after much of the recovery had already occurred.

Standing outside that Chicago building, I felt grateful for the legacy of rigorous thinking that continues to shape how we invest today. But the principles that emerged from those halls decades ago remain as relevant now as ever: markets work, diversification matters, costs compound, and behaviour determines outcomes.

The challenge isn’t knowing what to do—science has answered that. The challenge is doing it consistently, especially when markets test our resolve. That’s where good advice becomes invaluable.

Nick Stewart

(Ngāi Tahu, Ngāti Huirapa, Ngāti Māmoe, Ngāti Waitaha)

Financial Adviser and CEO at Stewart Group

---

References

 [1] The Nobel Prize, “Eugene F. Fama - Facts,” 2013, [nobelprize.org](http://nobelprize.org)

 [2] University of Chicago Booth School of Business, “Douglas W. Diamond Wins Nobel Prize in Economic Sciences,” October 2022, [chicagobooth.edu](http://chicagobooth.edu)

 [3] Dimensional Fund Advisors, “Leadership and Board of Directors,” [dimensional.com](http://dimensional.com)

 [4] Dimensional Fund Advisors SEC Form ADV, showing $835.7 billion in discretionary assets under management as of March 31, 2025

 [5] Morningstar, “Mind the Gap: The Behavior of the Average Investor,” various years, [morningstar.com](http://morningstar.com)

 [6] University of Chicago News, “Alumnus David Booth gives $300 million; University of Chicago Booth School of Business named in his honor,” November 2008, [news.uchicago.edu](http://news.uchicago.edu)​​​​​​​​​​​​​​​​