Putting a set amount into investments at regular intervals regardless of price is a mechanical approach that removes timing decisions from the equation. Here's how it works and why it tends to surface when markets swing.
When someone invests a fixed amount on a fixed schedule — rather than trying to pick the best moment to put a lump sum in — that approach is called dollar-cost averaging. The idea is simple: buy more units when prices are low and fewer when prices are high, without trying to guess when those turning points will arrive.
It is a mechanical rule rather than a market prediction. There is no judgement about whether valuations are attractive or whether a given day represents a good entry point. The schedule does the work instead.
How it works in practice
Consider an investor who puts $500 into a diversified fund on the first of every month. In month one the unit price is $2, so $500 buys 250 units. In month two the price falls to $1.50 — the same $500 now buys roughly 333 units. By month three the price recovers to $1.75, buying about 286 units.
Over those three months the average price paid per unit was around $1.71, which is below the arithmetic mean of the three prices ($1.75), and below the highest point. The investor bought more of the falling asset automatically, without needing to act on the decline.
The NZX50 has provided regular examples of this pattern. On some days the index finishes higher, on others lower — as interest.co.nz's regular market summaries track. A consistent monthly investor ignores those daily moves and accumulates units through the fluctuations.
Why it tends to get attention when markets are volatile
Recent moves in global equity markets have brought the approach back into focus. SpaceX's shares, for example, fell from above US$200 shortly after their June 2026 listing to around US$135, according to RNZ reporting. Investors who bought at the IPO price and held through the drop experienced the full swing. An investor using a fixed-schedule approach would have bought at both prices, smoothing the entry points.
The same dynamic plays out in KiwiSaver, where contributions flow in from employers and members every pay period regardless of what the market is doing that week. Over a career, those regular flows accumulate units across many market cycles — some at peaks, many at troughs.
What it does not do
Dollar-cost averaging does not guarantee a profit. If prices fall continuously over the entire investment horizon, a regular investor will keep buying into a declining asset. The approach reduces the average cost only when prices oscillate; in a sustained downward trend it delays losses rather than preventing them.
It also does not eliminate volatility exposure. A portfolio built through dollar-cost averaging is still fully exposed to the assets it holds. The mechanic addresses entry-point timing, not the risk characteristics of the underlying investment.
The opportunity cost question
A persistent debate in investment literature concerns whether dollar-cost averaging actually outperforms lump-sum investing. Academic work generally finds that lump sums tend to outperform over long horizons in rising markets, because more capital is invested sooner. Dollar-cost averaging lags when markets trend upward consistently — the investor misses the early gains by definition, since only part of the capital is deployed at the outset.
The practical case for dollar-cost averaging is less about maximising returns and more about consistency and behaviour. For most people, a regular contribution is more sustainable than accumulating a lump sum and then deciding when to invest it all at once. The mechanical nature removes the temptation to wait for a better entry point that may never arrive.
Whether through a KiwiSaver scheme, a managed fund, or a direct share portfolio, the regularity of the commitment is what defines the approach — not the amount, the asset class, or the specific timing.
This article is for general information only and is not personalised financial advice. Seek advice from a licensed financial adviser (registered on the FSPR) for guidance specific to your situation.