dollar cost averaging

Dollar cost averaging is a timing strategy of investing equal dollar amounts regularly and periodically over specific time periods (such as $100 monthly) in a particular investment or portfolio. By doing so, more shares are purchased when prices are low and fewer shares are purchased when prices are high. The point of this is to lower the total average cost per share of the investment, giving the investor a lower overall cost for the shares purchaced over time.^[1]

Dollar cost averaging is also called DCA and constant dollar plan in the US, pound-cost averaging in the UK, and by the currency-neutral term cost average effect^[2].

Parameters

In dollar cost averaging, the investor decides on three parameters: the fixed amount of money invested each time, and investment frequency, and the time horizon over which all of the investments are made. With a shorter time horizon, the strategy behaves more like lump sum investing. One study has found that the best time horizons when investing in the stock market in terms of balancing return and risk have been 6 or 12 months.^[3]
One key component to maximizing profits is to include the strategy of buying during a downtrending market, using a scaled formula to buy more as the price falls. Then, as the trend shifts to a higher priced market, use a scaled plan to sell. Using this strategy, one can profit from the relationship between the value of a currency and a commodity or stock.

Return

Assuming that the same amount of money is invested each time, the return from dollar cost averaging on the total money invested is^[4]

where p_F is the final price of the investment and is the harmonic mean of the purchase prices. If the time between purchases is small compared to the investment period, then can be estimated by the harmonic mean of all the prices within the purchase period.

Criticism of DCA Risk Reduction Theory

While some financial advisors such as Suze Orman ^[5] claim that DCA reduces exposure to certain forms of Financial risk associated with making a single large purchase, others such as Timothy Middleton claim DCA is nothing more than a marketing gimmick and not a sound investment strategy^[6].
Middleton claims that DCA is a way to gradually ease worried investors into a market, investing more over time than they might otherwise be willing to do all at once. Others supporting the strategy suggest the aim of DCA is to invest a set amount; the same amount you would have had you invested a lump sum.^[7]

Analysis supporting dollar cost averaging has been criticized because it often ignores transaction fees,^{[dubious – discuss]} which can be substantial. Numerous^{[citation needed]} studies of real market performance, models, and theoretical analysis of the strategy have shown that in addition to having the admitted lower overall returns, DCA does not even meaningfully reduce risk when compared to other strategies, even including a completely random investment strategy. ^[8]

Confusion

Discussions of the problems with DCA can do a disservice to investors who confuse DCA with continuous, automatic investing. Unfortunately this confusion of terms is perpetuated by many sources discussing automatic investing. (such as AARP^[9] and Motley Fool^[10]) The weakness of DCA arises in the context of having the option to invest a lump sum, but choosing to use DCA instead. Because the market trends upwards over time DCA always faces a statistical headwind: the investor is choosing to invest tomorrow rather than today, even though on average tomorrow's prices will be higher. DCA generally does not overcome this headwind. But most individual investors, especially in the context of retirement investing, never face a choice between lump sum investing and DCA investing with a significant amount of money. The disservice arises when these investors take the criticisms of DCA to mean that timing the market is better than continuously and automatically investing a portion of their income as they earn it. For example, stopping one's retirement investment contributions during a declining market on account of the (valid) statistical arguments against DCA would indicate a misunderstanding of those arguments. The demonstrable statistical weaknesses of DCA do not arise because attempts at timing the market tend to be effective, but because investing in the market today tends to be better than waiting until tomorrow. Applying that knowledge to the average retirement investor's situation would actually support - rather than contest - a policy of continuous, automatic investing without regard to market direction.

References

1. ^ Chartered Retirement Planning Counselor Professional Designation Program, College for Financial Planners, Volume 9, page 64
2. ^ "Durchschnittskosteneffekt". http://de.wikipedia.org/wiki/Durchschnittskosteneffekt. Retrieved on 2009-01-12. 
3. ^ Jones, Bill. "Do Not Dollar-Cost-Average for More than Twelve Months". http://www.efficientfrontier.com/ef/997/dca.htm. Retrieved on 2009-01-05. 
4. ^ "Derivation of the dollar cost averaging return formula". http://tsp.peacefulgains.com/Derivation-of-the-dollar-cost-averaging-return-formula/. Retrieved on 2009-01-05. 
5. ^ http://www.suzeorman.com/dt/calc_dollarcostaverage1.cfm
6. ^ Middleton, Timothy (2005-01-04). "The costly myth of dollar-cost averaging". http://moneycentral.msn.com/content/P104966.asp. Retrieved on 2009-01-05. 
7. ^ "Dollar Cost Averaging: A Technique that Drastically Reduces Market Risk". http://beginnersinvest.about.com/cs/newinvestors/a/041901a.htm. Retrieved on 2009-03-22. 
8. ^ Knight, John R.; Lewis Mandell (10 April 2002). "Nobody gains from dollar cost averaging analytical, numerical and empirical results". Financial Services Review (Elsevier Science Inc.) 2 (1). http://www.sciencedirect.com/science/article/B6W4D-45JK782-6/2/bec35bbe850cf520ddbb20d9eb634271. 
9. ^ "The hidden benefit of an automatic investing program". http://www.aarpfinancial.com/content/YourGoals/savForRet_hdnBenefitAutoInvest.cfm. Retrieved on 2009-05-02. 
10. ^ "Don't Make a Million-Dollar Mistake". http://www.fool.com/investing/mutual-funds/2008/12/21/dont-make-a-million-dollar-mistake.aspx. Retrieved on 2009-05-02. 

• The Intelligent Investor: revised 1972 edition Benjamin Graham, Jason Zweig. Collins, 2003. ISBN 0-06-055566-1
• Investopedia