Lump Sum vs Dollar-Cost Averaging: What the Evidence Says

The question

Imagine you receive €60,000 from an inheritance, a bonus or the sale of a property, and you want to invest it for the long term. You can invest it all today — a lump sum — or invest a fixed amount every month, say €5,000 a month for a year, which is called dollar-cost averaging, or cost averaging. Both end with the money invested. The question is which tends to leave you better off.

This is a different situation from investing part of your salary every month. If you invest as you earn, you are not choosing to average in; you simply invest money as it arrives, which is exactly what you should do. The choice only arises when you already have the money.

What the research found

Vanguard has studied the question twice. In 2012 its researchers compared investing a lump sum immediately with spreading it over 12 months in the United States, the United Kingdom and Australia, and found that the lump sum came out ahead about two-thirds of the time. Against spreading it over 36 months, the lump sum won about 90% of the time. In 2023 Vanguard repeated the exercise with global shares from 1976 to 2022 and found that the lump sum beat a year of cost averaging 68% of the time.

Other studies point the same way. An analysis published by the American Association of Individual Investors in 2025 found that a lump sum won 73% of the time over rolling periods since 1926. The pattern is consistent across countries and decades.

Why the lump sum usually wins

Shares have historically risen in more years than they have fallen, and over long periods they have returned more than cash. Money waiting to be invested sits in cash, earning less, while the market more often than not moves up. The longer you spread your purchases, the more time your money spends waiting, so the cost of averaging in tends to grow with the length of the plan.

Cost averaging does not improve your expected return. It buys you protection against regret, and that protection has a price.

Why many people still spread it out

A lump sum wins most of the time, not all of the time. In the roughly one-third of periods when markets fell soon after the money went in, averaging in did better, sometimes by a lot. One study, by the investment firm NDVR, found that in the worst third of historical scenarios, $100 invested at once fell to about $57, while $100 averaged in fell to about $74. If seeing a large investment drop sharply in its first months would make you sell in panic, a plan that spreads the risk may be the better plan for you — because a strategy you abandon at the bottom is worse than either.

A sensible middle way

• Decide first how much risk you want: the split between shares, bonds and cash matters far more than the timing of your purchases.
• If you can live with the ups and downs, investing the whole amount in a diversified portfolio has historically had the better odds.
• If you want to average in, keep the period short — three to six months — and write the schedule down so you do not start trying to time the market.
• Keep the waiting money somewhere safe that pays interest, such as a savings account or a money market fund.

Whatever you choose, make sure your emergency fund is in place first, and invest in low-cost, diversified funds rather than a few individual shares. This guide is general education, not personal financial advice.

This article is educational and general in nature. It isn’t personalized investment, tax, or legal advice — always weigh your own circumstances, or talk to a licensed professional, before making financial decisions.

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