Conventional investment wisdom suggests that dollar cost averaging is a good approach to allocating investment dollars over time. By always investing a constant dollar amount, the strategy ensures that fewer shares will be bought as prices rise, while more shares are purchased if prices decline, bringing down the average cost per share in the long run. The only question is over what time horizon it’s best to average in.
Yet as it turns out, the answer is “none”. In reality, a dollar cost averaging investment strategy doesn’t actually enhance returns in volatile markets that have similar upside gains and downside losses on a percentage basis. And given that on average, markets go up more often than they go down, choosing to dollar cost average is more likely to just leave gains on the table (and the longer the time period, the greater the risk of foregone returns).
However, while dollar cost averaging may not be likely to enhance returns in the long run, it is still a risk management technique. Over the dollar cost averaging time period itself, the diversification of the “new” investment and “old” investment may actually produce superior risk-adjusted returns. And given that the pain of losses is more severe than the joy of gains, risk-averse investors may prefer to dollar cost average simply to minimize the potential regret of not doing so and seeing markets decline shortly thereafter.
Nonetheless, for investors who are comfortable with the risk of their portfolios, and aren’t specifically seeking a “regret aversion” (or at least, regret minimization) strategy, in the long run the best time horizon for dollar cost averaging is simply to invest all the money immediately – at least, presuming the investment was desirable to own in the first place!