Market Structure·Line·4 Jun 2026
Passive Flows and S&P 500 Concentration Are Moving Together
Passive fund share of US equity AUM (%) and S&P 500 top-10 holdings weight (%), 2010–2024
Source Morningstar US Fund Flow Reports; Investment Company Institute (ICI); S&P Global Index Factsheets; Vanguard Investor Relations
Method Passive share represents estimated proportion of total US equity AUM held in index-tracking funds and ETFs. Top-10 weight is the combined weighting of the ten largest constituents of the S&P 500 index at year-end. Values are approximate annual snapshots pending full monthly data verification.