IXI Data
Indexing Inclusion Ratio (v8) — Stock-Level Indexed Ownership, January 2002 to December 2023
A monthly stock-level measure of indexed ownership built from FactSet fund holdings: the shares held by index funds plus the part of each active fund's portfolio that overlaps its benchmark.
Total indexed capital
$13.5T
December 2023, PP + AS
Avg. indexed ownership
25.6%
Value-weighted IXI, December 2023
Stocks covered
13,103
CRSP common shares, monthly
Sample period
2002–2023
1.28 M stock-month observations
Explore
Browse IXI by Stock
Select a stock to see its indexed ownership over time. The split shows how much comes from index funds (PP) and how much from the part of active funds' portfolios that overlaps their benchmarks (AS).
Loading stock data…
Aggregate Trend
The Rise of Indexed Ownership
The value-weighted mean IXI rose from 8.5% in January 2002 to 25.6% in December 2023. By then, about 26 cents of every dollar of U.S. common stock was held by index funds or by the part of active portfolios that overlaps a benchmark.
Monthly cross-sectional mean IXI. Solid: value-weighted. Dashed: equal-weighted. Shaded band: interquartile range.
Construction
Index Funds and the Index Inside Active Funds
IXI has two parts. PP is the shares held by index funds. AS is the part of each nominally active fund's portfolio that overlaps its benchmark. In January 2002, active-fund overlap (6.0% of market equity) exceeded index-fund ownership (2.6%). By December 2023, index funds held 19.4% and active-fund overlap added 6.3%.
Value-weighted shares of U.S. common-stock market equity, monthly. The total height of the two areas is the value-weighted mean IXI.
Key Findings
What the Data Shows
Cross-Section Shift, 2002–2023
Share of stocks at or below each level of IXI, December cross-sections. In 2002, 78% of stocks had IXI below 5%. By 2023, 32% were above 20% and 14% above 30%.
Top 20 Most Indexed Stocks (≥ $5B), Dec 2023
The most indexed stocks are mid-sized firms, not the largest. Among stocks worth at least $5 billion, the top twenty have IXI between 37% and 44%, against 26% for the largest fifth of stocks.
IXI vs. Benchmarking Intensity (BMI)
BMI (Pavlova and Sikorskaya 2023) counts every benchmarked dollar. IXI counts index-fund holdings and only the part of active portfolios that overlaps the benchmark, so it sits below BMI; the gap narrows as index funds grow. Equal-weighted June means over stocks covered by both; both means dip in 2008, when the matched sample grows from 2,919 to 3,908 stocks.
Download
IXI Panel Data
Monthly stock-level IXI (v8) for U.S. common stocks, January 2002 to December 2023.
Columns (full panel)
| Column | Description |
|---|---|
permno | CRSP permanent security identifier. |
permco | CRSP permanent company identifier. |
period | Month (first calendar day, YYYY-MM-DD). |
pp_share | Index-fund ownership (PP): shares held by index funds, as a fraction of CRSP market equity. |
as_share | Active-fund benchmark overlap (AS): for each nominally active fund, its assets times the smaller of its portfolio weight and its benchmark's weight in the stock, summed across funds, as a fraction of CRSP market equity. |
fund_branch_share | IXI, the main measure: PP plus AS, capped at one. Range 0–1. |
Construction Note
IXI is built from FactSet holdings of mutual funds and ETFs. Each fund is matched to the benchmark whose weights its holdings overlap most, with the assignment refreshed quarterly. Index funds contribute their positions in full (PP). A nominally active fund contributes its assets times the smaller of its portfolio weight and the benchmark weight in each stock, so only the part of its portfolio that overlaps the benchmark counts (AS). Stock-level IXI is PP plus AS divided by CRSP market equity, capped at one. Holdings enter only once they are public, so the measure carries no look-ahead. The universe is CRSP common shares (share codes 10, 11, 12 and 18) listed on the NYSE, AMEX and NASDAQ. See Behmaram (2026) for full construction details.
Citation
If you use the IXI data, please cite the source paper:
Behmaram, Pouya (2026). "The Price of Passive Ownership." Working Paper, ESG UQAM.
SSRN: https://ssrn.com/abstract=4996354BibTeX
@article{behmaram2026price,
title={The Price of Passive Ownership},
author={Behmaram, Pouya},
journal={Working Paper, Available at SSRN 4996354},
year={2026}
}The IXI panel data is currently available by request. To obtain access, please send an email describing your intended use.
Request Data Access