In his recent MultiFactorWorld post, Jared Kizer makes the case that despite U.S. equities' substantial out-performance in recent years, broad global diversification likely remains the correct approach for most investors. Based on the US and Global markets performance relative performance over time, there does not appear to be a reason to expect the U.S. equity market to systematically outperform other global markets over longer-term, though there will likely be extended periods when each under-performs the other. Read more here.
The above is not intended as investment advice or recommendation. Please consult an investment professional for advice that is suitable for your individual needs.