What Is Market Timing? Why It Rarely Works for Investors

Market timing is the practice of moving money in and out of investments based on predictions about where prices are heading. The goal is simple: sell before a fall, buy before a recovery, and pocket the difference. It sounds logical. In practice, the evidence overwhelmingly shows it destroys wealth for the people who attempt it.

This matters most for long-term investors, anyone approaching retirement, and people facing a lump-sum decision, such as reinvesting the proceeds of a property sale or choosing where to place a large KiwiSaver balance after switching providers. These are the moments when the temptation to wait for a "better" entry point is strongest and the cost of getting it wrong is highest.

How market timing is supposed to work

Investment markets move in cycles. Prices rise, fall, and recover over months and years. A successful market timer would exit near the top of each cycle, hold cash through the decline, then reinvest near the bottom. To pull this off, an investor needs to be right twice: the exit and the re-entry. Getting one of those calls wrong is enough to turn a profitable idea into a costly mistake.

The appeal is understandable.

When share prices are falling, sitting in cash feels safer. When headlines warn of recession or rising interest rates, selling feels prudent. But every piece of information an investor reacts to is already priced in by the time they act. Markets are ferociously efficient processors of news. By the time a retail investor in New Zealand reads a headline about the US Federal Reserve or the RBNZ and places a trade, professional participants have long since adjusted their positions.

What the research actually shows

The data on market timing is extensive and remarkably consistent across decades and geographies. Three bodies of evidence stand out.

The cost of missing the best days. Vanguard's Investment Advisory Research Centre has tracked what happens when investors step out of the market and miss its strongest days. Using S&P 500 data from 1988 to 2024, a US$100,000 portfolio left fully invested grew to roughly US$4.9 million. Missing just the 10 best trading days over those 37 years cut the ending value to US$2.3 million. Missing 30 of the best days reduced it to US$900,000. The critical insight is the best days and the worst days tend to cluster together. An investor who sells during a sharp fall is very likely to be sitting in cash when the sharpest recoveries occur. For a KiwiSaver member in a growth fund, the principle is identical: the strongest recovery days for a diversified growth portfolio typically arrive within weeks of the worst ones.

720 timing approaches tested, almost all failed. Dimensional Fund Advisors simulated 720 distinct timing approaches across multiple markets, premiums, signals, and rebalancing frequencies. Of those, just 30 produced outperformance in backtesting. The catch: each successful approach was acutely sensitive to its specific parameters. Tweaking a single input, such as the rebalancing frequency or breakpoint threshold, caused outperformance to collapse. The researchers concluded the handful of "winning" approaches were statistically indistinguishable from chance. Given enough combinations, some will always look good in hindsight.

Investors consistently underperform the markets they invest in. DALBAR, an independent US research firm, has tracked the gap between market returns and actual investor returns since 1985. Its 2025 report found the average US equity fund investor earned 16.54% in 2024, while the S&P 500 returned 25.02%. Over 20 years to December 2024, the average equity investor earned 9.24% per annum compared with 10.35% for the index. The performance gap is not caused by picking the wrong funds. It is caused by buying and selling at the wrong times. DALBAR's "Guess Right Ratio" for 2024 fell to just 25%, meaning investors correctly timed their flows only one quarter of the time. While these are US figures, the behavioural patterns are universal. We see the same dynamics play out in New Zealand, where investors switch KiwiSaver Schemes after a downturn or move to conservative funds right before a recovery.

Why market timing feels so tempting

Part of the reason market timing persists is the illusion of control. Markets are inherently uncertain, and doing nothing during a fall feels reckless. Placing a trade, even a poorly timed one, replaces uncertainty with action, and action feels like progress. Combine this with loss aversion (the psychological tendency to feel losses roughly twice as acutely as equivalent gains) and survivorship bias (the lucky exits get amplified; the far more numerous mistimed moves remain invisible), and you have a powerful recipe for poor decision-making.

In our advisory work across New Zealand, we see several recurring patterns. Investors sell during a downturn, intending to buy back in once things "settle down." By the time markets feel calm, much of the recovery has already happened. Others sit in cash after selling a rental property, waiting for the OCR to signal direction before committing to a diversified portfolio. Some switch their KiwiSaver to a conservative fund after a sharp market fall, then never switch back. Each of these decisions feels prudent in the moment. Each comes with a measurable long-term cost.

If you've recently sold an investment, switched funds, or are sitting in cash wondering when to re-enter the market, a conversation with one of our advisers can help you think through the next step.

What works instead

The alternative to market timing is a structured, evidence-based approach to staying invested through full market cycles, combined with regular review and adjustment. "Staying invested" means resisting the urge to make reactive changes while maintaining the discipline to rebalance, review risk settings, and adapt your plan as your circumstances change.

Dollar-cost averaging removes the need to pick the right entry point. By investing a fixed amount at regular intervals, investors buy more units when prices are low and fewer when prices are high. Over time, this smooths the effect of volatility and reduces the risk of committing a lump sum at the worst possible moment. For KiwiSaver members making regular contributions through their salary, this is already happening by default.

Diversification across asset classes means no single market event can devastate a portfolio. A well-constructed portfolio holds a mix of growth assets (equities, listed property) and defensive assets (bonds, cash) calibrated to the investor's goals and time horizon. This is the core of what a sound investment management programme delivers.

A financial plan built around your goals provides the framework to hold steady when markets are volatile. Investors who understand how their portfolio connects to specific outcomes, whether funding retirement, helping children into their first home, or building long-term wealth, are far more likely to stay the course. A plan turns market noise into context rather than cause for action.

Regular rebalancing is the disciplined counterpart to market timing. When one asset class outperforms, rebalancing trims the winner and tops up the laggards, maintaining the portfolio's intended risk profile. It is a systematic way of buying low and selling high without requiring any prediction about future prices.

Why Market Timing Rarely Works for Investors

The investors who build wealth over time are the ones who stay invested, keep costs low, diversify sensibly, and review their plan periodically rather than react to headlines.

For those approaching or already in retirement, this discipline matters even more. Retirement planning structured around reliable income sources and prudent drawdown rates can weather market cycles without requiring the investor to predict them.

Our role is to help people make clear-headed investment decisions, particularly when markets are making it difficult to think clearly. If you'd like to talk through how your investments are positioned for the years ahead, book a conversation with our team.