S&P 500's 10 Largest Positions Make Up 38.44% of Index

The S&P 500’s 10 largest positions accounted for 38.44% of the benchmark in an index-weight snapshot, placing more than a third of its weight in a small group of holdings.

The 38.44% figure describes their share of the index; it does not measure how much those holdings contributed to its returns.

A separate measure shows a gap between the benchmark and its typical member. The equal-weight S&P 500 lagged the standard index by about 6% over six months, while the median constituent stood about 15% below its 52-week high.

The figures measure different things: the concentration of the largest positions, the performance gap between two versions of the index, and the distance of a typical stock from its own high. The available figures do not establish how much the largest positions contributed to the six-month gap.