March 6 (Reuters) - S&amp;P Dow Jones Indices said on Friday that data center equipment maker Vertiv (VRT.N) , photonics product makers Lumentum (LITE.O) and Coherent (COHR.N) , and telecom company EchoStar (SATS.O) will join its flagship S&amp;P 500 (.SPX) index.
The S&amp;P 500, widely regarded as the benchmark for U.S. large-cap stocks, is tracked by trillions of dollars in index and exchange-traded funds, making changes to its membership closely watched by investors. Here is an overview of the change to the index and stock reaction:
<ul>
<li>Vertiv shares jumped nearly 6% in extended trading on the news, while EchoStar rose about 4%</li>
<li>Companies added to the S&amp;P 500 often see their shares rise as index-tracking funds buy the stock to replicate the benchmark, boosting demand and liquidity.</li>
<li>Lumentum and Coherent were also last up 1.7% and 0.4%, respectively, after the bell</li>
<li>The new entrants will replace dating platform Match Group (MTCH.O) , managed care company Molina Healthcare (MOH.N) , food processor Lamb Weston (LW.N) and payroll software maker Paycom (PAYC.N) .</li>
<li>Companies removed from the index can come under selling pressure as those same funds sell the shares to rebalance their portfolios.</li>
<li>Paycom was last down 3% after the bell, while Match Group declined 0.7% and Molina slipped marginally.</li>
<li>S&amp;P Dow Jones Indices said the changes will take effect before the market opens on March 23 as part of the quarterly rebalance.</li>
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S&P Dow Jones Indices announced that Vertiv, Lumentum, Coherent, and EchoStar will join the S&P 500 index on March 23. Following the announcement, Vertiv's shares rose nearly 6%, and EchoStar's shares increased about 4%. Lumentum and Coherent also saw slight gains. The new additions will replace Match Group, Molina Healthcare, Lamb Weston, and Paycom, which experienced declines in their stock prices. The changes are part of the quarterly rebalance of the index, closely monitored by investors.

- S&P Dow Jones Indices announced that Vertiv, Lumentum, Coherent, and EchoStar will join the S&P 500 index, effective March 23.  
- Vertiv's shares rose nearly 6% and EchoStar's by about 4% on the news, reflecting increased demand as index-tracking funds purchase these stocks.  
- Replacements for Match Group, Molina Healthcare, Lamb Weston, and Paycom may face selling pressure, with Paycom down 3% and Match Group declining 0.7% after hours.

Vertiv, Lumentum, Coherent, EchoStar set to join S&P 500