S&P 500 Rebalance: Equity Strategy Notes on the September Changes

NEW YORK — S&P Dow Jones Indices announced on September 4, 2026, that Bloom Energy, Illumina and Everpure would join the S&P 500 as part of its quarterly rebalance, effective before the market opened on September 21. The announcement, which also reshuffled the S&P 100, S&P MidCap 400 and S&P SmallCap 600, offers a useful set of notes for equity strategy because index membership reflects how the market’s composition has shifted.

The index provider said the changes were intended to make each index more representative of its market capitalization range.

Who moved in and out

Joining the S&P 500 were Bloom Energy, classified in Industrials; Everpure, in Information Technology; and Illumina, in Health Care. Leaving the index were Molson Coors Beverage, from Consumer Staples; The Trade Desk, from Communication Services; and Builders FirstSource, from Industrials. All three departing companies were set to move to the S&P SmallCap 600.

Everpure and Illumina came from the S&P MidCap 400, which in turn added HubSpot, AGNC Investment, Corcept Therapeutics and Brinker International. The midcap index also removed Boston Beer and Capri Holdings.

The S&P 100 tilts further toward technology

The changes to the S&P 100, the index of the largest and most established companies in the S&P 500, carried a clear sector signal. Four companies were added: Dell Technologies, Palo Alto Networks, Arista Networks and Sandisk, all classified in Information Technology. Four were removed: Honeywell Aerospace, NIKE, Simon Property Group and Colgate-Palmolive, drawn from Industrials, Consumer Discretionary, Real Estate and Consumer Staples.

The swap is one of the clearer market themes in the announcement. Every addition came from a single sector, and every deletion came from a different one. The large-cap benchmark became more concentrated in technology hardware, networking and security.

Reading the S&P 500 changes

The S&P 500 additions are more varied. Bloom Energy brings a power generation company into the index. Illumina represents genomics within Health Care. Everpure adds another technology name.

The deletions are equally informative. Moving directly from the S&P 500 to the SmallCap 600, skipping the midcap index, is a sign that a company’s market value has declined well below the large-cap range. That applied to all three removed companies.

Sector arithmetic

Counting by sector, the S&P 500 changes were roughly balanced: Industrials gained Bloom Energy and lost Builders FirstSource, Information Technology and Health Care each gained a member, and Consumer Staples and Communication Services each lost one. The S&P 100 changes were not balanced at all. Information Technology gained four members while four other sectors each lost one. The difference between the two indexes is a useful reminder that the market’s largest companies have become more concentrated in technology than the broader large-cap universe.

Equity strategy implications

Index changes matter for markets mainly because of passive investing. Funds that track the S&P 500 must buy additions and sell deletions around the effective date, which can create concentrated trading on the day of the change. Those flows are mechanical and do not reflect a view on the companies’ prospects.

For investors setting equity strategy, the more durable lesson is about concentration. Each time large technology companies replace firms from other sectors in benchmark indexes, the sector weights of index funds shift accordingly. An investor who owns an S&P 100 or S&P 500 fund is, after this rebalance, slightly more exposed to technology than before. Investors who want a particular sector balance need to account for that drift.

The S&P 100 changes are a reminder that sector concentration in benchmarks is not static. It accumulates through decisions like these, one quarterly rebalance at a time.

What to watch

The changes were scheduled to take effect before the open on September 21, 2026, following the close of trading on the prior Friday, a date that typically coincides with heavy rebalancing flows. Beyond that date, the next quarterly rebalance in December will show whether the shift toward technology in the largest indexes continues.