Five Largest S&P 500 Companies Match Value of Bottom 434

The five largest S&P 500 companies had a combined market value equal to that of the index’s bottom 434 companies, highlighting the benchmark’s growing concentration in its biggest constituents.

Michael Batnick said in a post that the concentration was unlike anything previously experienced.

The S&P 500 uses market-cap weighting, which gives larger companies a greater influence on the index. Mega-cap technology companies and businesses tied to artificial-intelligence infrastructure have helped support the benchmark even as many lower-weighted constituents lagged.

The comparison follows weakness in S&P 500 breadth, with market gains concentrated among a relatively small group of large companies.