Michael Santoli

S&P's decision to add Tesla to the S&P 500 next month will force some mechanical selling by index funds of the other 499 stocks in the benchmark.

The S&P 500 has posted an annualized gain of about 10% for 2020, or 12% or so including dividends, right in line with the historical yearly average.

Can history help handicap where markets head from here after the extraordinary path stocks have taken so far this year?