There has been much discussion in the news recently about new nominal highs in stock indices like the Dow Jones Industrial Average and the S&P 500. When markets hit new highs, is that an indication that it’s time for investors to cash out? History tells us that a market index being at an all-time high generally does not provide actionable information for investors. For evidence, we can look at the S&P 500 Index for the better part of the last century.
From 1926 through the end of 2016 the proportion of annual returns that have been positive after a new monthly high is similar to the proportion of annual returns that have been positive after any index level. In fact, over this time period almost a third of the monthly observations were new closing highs for the index. Looking at this data, it is clear that new index highs have historically not been useful predictors of future returns. Given that the level of an index by itself does not seemingly have a bearing on future returns, you may ask yourself a more fundamental question: What drives expected returns for stocks?