Dollar-Cost Averaging, Lump Sum, or Scaling In?

Why this matters

An inheritance, a bonus, or savings that have built up in cash all raise the same question: invest it now, or ease in? It feels like an important decision, and people often agonize over it. This lesson shows what each choice actually does, so you can decide based on the tradeoffs rather than on a guess about next month.

Three methods

• Lump sum. Invest the whole amount right away.
• Dollar-cost averaging. Invest equal amounts at regular intervals, such as $1,000 a month for a year, whatever the price. You automatically buy more shares when prices are low and fewer when they're high.
• Scaling in. Buy part now and place orders to buy more at lower prices, as in the last lesson, Scaling Into a Position.

Note one thing these have in common: until money is invested, it's sitting in cash. That waiting has a cost when prices rise.

Try it

The tool invests $12,000 in STU Corp, a fictional company starting at $50, using each method. Pick a price path to see how each one finishes after 12 months.

Hypothetical prices for a fictional company. Dollar-cost averaging buys $1,000 at the start of each month. Scaling in buys $4,000 at once, with limit orders for $4,000 each at $48 and $46. Fractional shares are allowed. Cash waiting to be invested earns nothing here; in reality it would earn a little interest.

Price path	Lump sum	Dollar-cost averaging	Scaling in
Rises steadily, to $62	$14,880	$13,458	$12,960
Falls to $36, then recovers to $50	$12,000	$14,146	$12,514
Keeps falling, to $34	$8,160	$9,935	$8,510
Choppy, ends at $50	$12,000	$12,012	$12,514

Each method wins on some path. The lump sum wins when prices rise, because every dollar was invested for the whole climb. Spreading out wins when prices fall first, because later purchases are cheaper. In the rising case, scaling in left $8,000 uninvested, since its lower orders never filled.

What the evidence says about the odds

If every path were equally likely, the choice would be a coin toss. They aren't. Markets have risen in more years than they've fallen, so money that waits in cash usually misses some growth.

In a 2023 paper, Vanguard researchers compared investing a lump sum with spreading it out over time, using historical and simulated market data. They found that the lump sum outperformed roughly two-thirds of the time, and noted that over 1976 to 2022, US stocks beat cash 76% of the time and bonds beat cash 68% of the time.¹ They concluded that most investors, particularly those without a strong aversion to losses, should invest a lump sum immediately.¹

The same paper describes when spreading out still has a place. It's better than leaving the money in cash indefinitely, and by lowering risk temporarily it can limit the losses, and the regret, of investing everything right before a severe downturn. For a very loss-averse investor, that can help them stick with the plan.¹

Regular investing is different

Most people already dollar-cost average without choosing to: a 401(k) contribution from every paycheck invests money as it's earned. That isn't a decision to hold cash back. It's investing as soon as the money exists, which is exactly what the research favors. The lump-sum question only arises when you already have the full amount in hand.

Key takeaways

• Lump sum, dollar-cost averaging, and scaling in each win on some price paths and lose on others.
• Vanguard found that lump sums beat spreading out roughly two-thirds of the time, because markets have risen more often than not.
• Spreading out lowers short-term risk and regret, at the cost of lower expected returns. It beats staying in cash.
• Investing each paycheck as it arrives isn't holding money back; it's investing as soon as possible.

Check your understanding

Why has investing a lump sum usually beaten dollar-cost averaging in historical data?

1. Because buying everything at one price always gives the lowest average cost per share.
2. Because markets have risen more often than not, so cash waiting to be invested usually missed growth.
3. Because dollar-cost averaging charges higher fees on each of the smaller purchases made.

Sam has $30,000 in savings to invest and says, "If I put it all in and the market drops next month, I'll panic and sell." What fits the research best?

1. Keep it in cash until the market has fallen, then invest it all at the lower prices.
2. Invest it all at once anyway, since a lump sum is guaranteed to come out ahead.
3. Spreading it out over a set schedule can be reasonable, since it beats staying in cash.

What's next

Once you own a position, its price will move, and you'll be tempted to buy more of it. Adding to Winners and Averaging Down covers when that makes sense and when it doesn't.