Ten Companies, a Quarter of Institutional Equity
How much of institutional equity sits in just ten companies. Every quarterly SEC 13F filing since 2013 is aggregated by issuer, and the ten largest issuers' share of all reported long value is drawn under two definitions that agree — which is the point. A market where ten names were a tenth of institutional portfolios became one where they are more than a quarter, and the chart shows the climb was not one event but a thirteen-year grind.
What does it show?
Concentration did not arrive with the AI boom — the ten-name share has climbed almost monotonically since 2013, through three entirely different market regimes.
Methodology
Every quarterly SEC Form 13F structured dataset since 2013 is aggregated by (excluding the SEC's first, partial collection quarter) normalized issuer name, and the chart shows the value share of the ten largest issuers. Two definitions are drawn because they tell the same story: stand-alone reports exclude combination filings and reports listing other included managers, which removes most double counting from overlapping reporting structures, while the as-filed line keeps every effective holdings report. Values filed before January 2023 are converted from thousands of dollars, with a reconciliation against each filing's summary total catching the historical filings that reported in dollars. Restatement amendments replace the prior table; new-holdings amendments are appended. Form 13F covers reported long positions in U.S.-listed securities only: no short positions, cash, private assets, most foreign listings, or most derivatives. Reported value moves with prices as well as portfolio decisions. Issuer-name normalization cannot remove every filer abbreviation or corporate renaming. Obvious pooled products (index funds and ETFs) and option rows are excluded before aggregation.