Key Takeaways Palantir Technologies and Dell Technologies, along with Erie Indemnity, became members of the S&P 500 Index today.Palantir Technologies shares are trading at all-time highs.Dell's shares were lower in recent trading,

Palantir Technologies, Dell Technologies, and Erie Indemnity will begin trading on the S&P 500 today, Monday, September 23.

Palantir’s stock has outperformed the S&P 500 by a wide margin in recent years, but Raymond James has concerns about the stock’s valuation.

Palantir and Dell are joining the S&P 500 Monday along with Erie Indemnity, replacing a trio of stocks that are shifting to some of S&P Global's smaller indexes.