July and August have seen major US indexes reach repeated all-time highs. While it is preferred to buy low and sell high, there is no scientific method to accurately determine future markets. However, odds favor that all-time highs will soon be followed by new all-time highs. A new market high follows 80.4% of market highs from the previous year, with 19.8% average gains. Regardless of market timing, a long-term investment strategy has the highest probability of providing positive returns.

Sources: Dimensional, “S&P 500 Total Return Index Highs;” Google Finance