The three major indices featured in the table comprise the S&P Composite 1500 Index, which represents approximately 90% of total U.S. equity market capitalization (cap), according to S&P Dow Jones Indices. 

Large-cap stocks, as measured by the S&P 500 Index, have not only significantly outperformed their mid- and small-cap counterparts year-to-date through 9/23/20, they are in positive territory. 

With respect to large-caps, the top-performers were Information Technology, Consumer Discretionary and Communication Services, all of which are cyclical in nature. As it turns out, these three sectors were the beneficiaries of the shelter-at-home response to the COVID-19 pandemic, in our opinion. 

Sector performance can vary widely by market cap. Health Care is perhaps the only one that does not reflect an enormous disparity in performance (see table). 

With respect to where the three indices stood relative to their all-time highs as of the close on 9/23/20 (not shown in table), the S&P 500, S&P MidCap 400 and S&P SmallCap 600 Indices were down 9.60%, 14.91% and 25.10%, respectively, according to Bloomberg. That is actually a huge improvement over where they stood at the lowest point (3/23/20 for all three indices) during the COVID-19 sell-off. As of the close on 3/23/20, the S&P 500, S&P MidCap 400 and S&P SmallCap 600 Indices were down 33.92%, 42.14% and 45.77%, respectively, from their all-time highs.