N-PORT Holdings Concentration: Fund Registrants, Reported Value, and Coverage
A corrected review of 2.42 million N-PORT positions measures concentration across fund registrant CIKs, five periods, and asset categories.
The 31 March 2026 cohort contains 2,418,232 public Form N-PORT position rows across 1,194 registrant CIKs and 6,909 filing accessions. Reported value totals $22.97 trillion. The ten largest registrant aggregates account for 49.4 percent of reported value, while the largest fifty account for 75.4 percent. The top-ten share remains between 48.4 and 50.9 percent across five quarter-end periods. Common equity represents 75.7 percent of reported value, while debt represents 13.0 percent. These are fund portfolio holdings reported on Form N-PORT. They are not Form 13F manager positions, beneficial ownership, voting control, or complete institutional balance sheets.
1. Source correction and cohort rules
The source combines Form N-PORT and Form 13F rows. At the 31 March 2026 period end, N-PORT contributes 2,418,232 positions from 1,194 CIKs. Form 13F contributes 24,860 rows from six CIKs. The earlier article described the quarter-end cohort as 13F evidence, which was incorrect. This revision filters to N-PORT-P before calculating every headline value.
2. Positions, accessions, and registrants are different units
One position row records a holding reported within an accession. One registrant CIK can submit several accessions for separate funds or series. The cohort therefore contains 2,418,232 position rows, 6,909 accessions, and 1,194 CIKs. Concentration aggregates value by CIK, which groups the reporting structure above individual accessions. The result changes if value is grouped by series, fund, adviser, or beneficial owner.
3. Ten registrant aggregates report half the value
The ten highest-value CIK aggregates report $11.34 trillion, or 49.4 percent of cohort value. CIKs ranked eleven through fifty report $5.98 trillion, or 26.0 percent. The remaining 1,144 CIKs report $5.66 trillion, or 24.6 percent. The top fifty therefore account for 75.4 percent of reported value under the CIK aggregation rule.
4. Concentration remains stable across five period ends
The top-ten share is 48.4 percent in March 2025, 49.0 percent in June, 50.9 percent in September, 49.5 percent in December, and 49.4 percent in March 2026. The top-fifty share remains between 74.7 and 76.3 percent. Reported total value rises from $20.30 trillion to $22.97 trillion across the interval, with a September peak of $24.11 trillion.
5. Reported value covers several asset categories
Common equity category EC accounts for $17.39 trillion, or 75.7 percent of reported value. Debt category DBT accounts for $2.98 trillion, or 13.0 percent. Asset-backed and mortgage-backed category ABS-MBS accounts for $1.02 trillion, or 4.5 percent. Short-term investment vehicles account for $0.48 trillion, while missing asset-category values account for $0.33 trillion. The cohort is broader than long United States equity.
6. N-PORT and 13F answer different questions
Form N-PORT is a monthly portfolio-holdings report for registered management investment companies and certain exchange-traded funds. Form 13F is a quarterly holdings report for institutional investment managers meeting the statutory threshold for Section 13(f) securities. Mixing the forms changes filer populations, asset scope, reporting frequency, and the meaning of the CIK. The corrected analysis uses only N-PORT.
7. Supported interpretation
The record supports three conclusions under CIK aggregation. Public N-PORT value is concentrated, with the top ten registrant CIKs near half across five periods. Common equity accounts for three quarters of the March 2026 value, while debt and asset-backed categories remain material. The result measures reporting concentration among fund registrants. It does not measure market ownership, voting power, adviser control, beneficial ownership, or total institutional assets.
8. Limitations
One registrant CIK can represent several funds or series, and several accessions can share a report date. Reported values are fund-provided period-end values and can change through amendments. CUSIP is missing on some positions. The table does not provide a validated adviser-parent hierarchy or beneficial-owner map. The June 2026 period is incomplete and remains outside the five-period comparison.