Is dollar-cost averaging overrated?

Investing set amounts at regular intervals can reduce risk but may lead to lower returns compared with the lump-sum approach.

Adam Zoll 28 July, 2014 | 6:00PM

Question: Every year I add money to my RRSP account in a lump sum. Would I be better off using dollar-cost-averaging over the course of the year?

Answer: Dollar-cost-averaging, which is a technical term for buying shares of a stock or mutual fund in equal dollar amounts and at regular intervals, is assumed by many investors and financial pros to be the best way to invest. The advantages are clear: By investing a given amount over time and in equal-sized chunks rather than all at once, the investor ends up buying more shares when prices become cheaper and fewer when they become more expensive.

For example, let's say you get a $1,200 tax refund. Rather than invest all $1,200 at once, you could invest $100 per month for a year. Now let's say the fund you're investing in sells for $10 per unit in the first month but drops to $5 in the second. Using the dollar-cost averaging method, you would end up buying 10 units in the first month, before the market drop, but 20 units in the second, after the drop. Had you invested the entire $1,200 in the first month you would have owned 120 units, which, in month two, would have declined in value to $600. In this way, dollar-cost averaging helps reduce an investor's exposure to a potential market downturn, a danger inherent in the lump-sum approach.

Dollar-cost averaging also fosters a level of investing discipline. Rather than trying to figure out the best time to invest a lump sum, dollar-cost averaging uses a more systematic approach that helps investors conquer bad habits such as buying units only when the market is up.

If you have an employer-sponsored pension plan, you may be using dollar-cost-averaging without even knowing it. That biweekly or monthly contribution made to your pension is a form of dollar-cost-averaging.

Putting dollar-cost averaging to the test

However, despite the conventional wisdom that dollar-cost averaging is usually the best way to invest, there is an opportunity cost to be paid for holding money in cash while it waits to be invested in the market. If the market goes up while you're dollar-cost averaging into it, you've lost out on any gains you would have had by investing the entire amount right away.

In fact, a recent Vanguard study in the U.S. found that, on average, lump-sum investing resulted in higher returns than dollar-cost averaging about two-thirds of the time. The authors looked at historical monthly returns for US$1 million invested as a lump sum and through dollar-cost averaging over periods as short as six months and as long as 36 months, assuming that funds were kept in cash before being invested. They tested various stock/bond allocations ranging from an all-equities portfolio to an all-bond portfolio. Finally, they tested these variations on the dollar-cost averaging vs. lump-sum question over rolling 10-year periods from 1926-2011.

At the end of each 10-year period, the portfolio value of the lump-sum method was compared with that of the dollar-cost averaging method. The result: The lump-sum method delivered higher returns compared with the 12-month dollar-cost averaging method about 66% of the time regardless of whether an all-equities, all-bond, or 60% equity/40% bond allocation was used. When the authors conducted a similar analysis using historical returns for markets in the UK and Australia, a similar pattern emerged, with lump-sum investing consistently outperforming dollar-cost averaging.

The authors note that the longer the dollar-cost averaging time frame, the greater the chance of the lump-sum method outperforming. For example, dollar-cost averaging over 36 months lost out to the lump-sum method 90% of the time (for U.S. markets).

It's also worth noting that while lump-sum investing consistently outperformed dollar-cost averaging, the average rate of outperformance was relatively modest. Using a 60/40 equity-bond allocation in U.S. markets and dollar-cost averaging over a period of 12 months, the authors found that after 10 years the initial US$1 million investment would have grown to US$2,450,264 on average using the lump-sum method versus US$2,395,824 using dollar-cost averaging, a difference of about US$54,000 or 2.3%.

DCA better in declining markets

So the Vanguard study proves it's always best to invest in a lump sum if possible, right? Not so fast. As the authors concede, during market declines, the dollar-cost averaging method often performs better because it helps mitigate the effects of falling unit prices, whereas the lump-sum method puts all the capital at risk in the market at once. They examined more than 1,000 rolling 12-month periods in U.S. markets and found that lump-sum investors would have seen their investment decline in value 22.4% of the time vs. 17.6% for dollar-cost averaging.

The takeaway

So what should we make of these findings? There appears to be little doubt that, when investing for the long-term, you are more likely to end up ahead using the lump-sum approach than dollar-cost averaging. (Again, assuming you have a choice -- with a work-sponsored retirement account, you may not.) However, there are three important points in dollar-cost averaging's favour.

  • If you expect a market downturn in the near future, dollar-cost averaging is the better choice. By spreading out contributions at regular intervals, you are essentially limiting your exposure by keeping some of your money in cash.

  • For some investors, a relatively modest shortfall in return is a small price to pay for peace of mind. If dollar-cost-averaging helps you sleep better at night than you would with an all-in strategy, it may be worth it.

  • Dollar-cost averaging, especially through an automatic contribution mechanism such as a company pension plan or automatic deduction from a bank account, offers a level of investing discipline that lump-sum investing doesn't. The lump-sum approach, by its nature, involves market timing, and that's a dangerous game to play, especially during times of volatility. Dollar-cost averaging provides a smoother, more consistent entry into the market.

One last factor to consider is investing costs, which may provide an advantage for the lump-sum method. For example, if using dollar-cost averaging requires paying multiple brokerage fees to buy shares of a stock in several lots rather than just once, this may further erode your returns as compared with the lump-sum method.

Ultimately, your comfort level with lump-sum investing and your expectations about the market's near-term direction should help you decide if it makes sense for you. If moving a lump sum into the market all at once gives you a queasy feeling in the pit of your stomach, that may be all the answer you need.

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Adam Zoll

Adam Zoll  Adam Zoll is an assistant site editor with