Mar 31, 2026 filings. Quarterly 13F reports arrive up to 45 days after quarter end; this register is filed through May 29, 2026.
255 institutional managers reported holding IOSP for the quarter ended Mar 31, 2026. Reported positions total over 95% of shares outstanding; the top 10 hold 60%. 34 opened new positions; 35 closed out. Complete ranked register from SEC 13F filings.
| manager | shares | % out | value (Mar 31, 2026 close) | change | held since |
|---|---|---|---|---|---|
| BlackRock | 3.88M | 15.61% | $283.2M | added +5.9% | ≤2013 |
| Vanguard Group | 3.17M | 12.76% | $231.5M | added +1.6% | ≤2013 |
| Allspring Global Investments Holdings, LLC | 2.32M | 9.32% | $169.1M | trimmed -1.7% | 2021 Q4 |
| Dimensional Fund Advisors | 1.24M | 5.00% | $90.7M | added +5.7% | ≤2013 |
| State Street | 964.3k | 3.88% | $70.4M | added +1.6% | ≤2013 |
| Victory Capital Management INC | 865.0k | 3.48% | $63.1M | trimmed -9% | 2019 Q1 |
| Nuveen | 643.2k | 2.59% | $47.0M | added +28% | 2019 Q2 |
| UBS | 640.4k | 2.58% | $46.7M | added +190.1% | ≤2013 |
| Geode Capital | 630.6k | 2.54% | $46.0M | added +3.5% | ≤2013 |
| Two Sigma | 593.0k | 2.39% | $43.3M | added +271.8% | 2021 Q1 |
| Goldman Sachs | 492.0k | 1.98% | $35.9M | added +1.5% | ≤2013 |
| Assenagon Asset Management S.a. | 490.9k | 1.98% | $35.8M | added +175.5% | 2023 Q3 |
| Qube Research & Technologies LTD | 406.6k | 1.64% | $29.7M | added +26.9% | 2022 Q4 |
| Charles Schwab Investment Management | 365.9k | 1.47% | $26.7M | trimmed -2.1% | ≤2013 |
| AQR Capital | 312.1k | 1.26% | $22.8M | added +16.4% | 2021 Q3 |
| Brown Advisory INC | 296.5k | 1.19% | $21.6M | trimmed -3.1% | 2025 Q1 |
| Gendell Jeffrey L | 294.5k | 1.19% | $21.5M | added +3.2% | 2024 Q1 |
| Bank OF America CORP /DE/ | 290.8k | 1.17% | $21.2M | trimmed -9.8% | ≤2013 |
| D. E. Shaw | 286.8k | 1.15% | $20.9M | trimmed -7.5% | ≤2013 |
| Northern Trust | 284.2k | 1.14% | $20.7M | added +3.5% | ≤2013 |
| Royce & Associates | 261.3k | 1.05% | $19.1M | trimmed -14.4% | ≤2013 |
| Morgan Stanley | 235.6k | 0.95% | $17.2M | trimmed -3.3% | ≤2013 |
| Western Standard LLC (focused) | 226.8k | 0.91% | $16.6M | trimmed -15.5% | 2025 Q3 |
| Citadel Advisors | 220.9k | 0.89% | $16.1M | added +203.9% | ≤2013 |
| SEI Investments CO | 174.1k | 0.70% | $12.7M | added +67.9% | 2021 Q4 |
| Point72 | 166.8k | 0.67% | $12.2M | added +74.2% | 2022 Q1 |
| First Wilshire Securities Management INC | 148.1k | 0.60% | $10.8M | added +47.2% | 2025 Q4 |
| Janus Henderson | 133.3k | 0.54% | $9.7M | trimmed -11.7% | 2019 Q1 |
| BNY Mellon | 131.3k | 0.53% | $9.6M | trimmed -4.7% | ≤2013 |
| HRT Financial LP | 125.1k | 0.50% | $9.1M | added +6.9% | 2024 Q2 |
| Acadian Asset Management | 122.6k | 0.49% | $8.9M | added +765.5% | 2018 Q2 |
| Hotchkis & Wiley Capital Management LLC | 120.8k | 0.49% | $8.8M | trimmed -3.4% | 2023 Q3 |
| Principal Financial Group INC | 120.5k | 0.48% | $8.8M | added +2% | ≤2013 |
| Panagora Asset Management INC | 119.7k | 0.48% | $8.7M | added +45.8% | 2018 Q4 |
| Renaissance Technologies | 118.9k | 0.48% | $8.7M | trimmed -1.2% | 2022 Q2 |
| Invesco | 118.1k | 0.47% | $8.6M | added +12.8% | ≤2013 |
| Voloridge Investment Management | 108.0k | 0.43% | $7.9M | trimmed -22% | 2024 Q2 |
| ZWJ Investment Counsel INC | 103.8k | 0.42% | $7.6M | added +9.8% | 2015 Q2 |
| Teacher Retirement System OF Texas | 103.1k | 0.41% | $7.5M | added +22.1% | 2020 Q4 |
| Jane Street | 94.5k | 0.38% | $6.9M | trimmed -13.3% | 2021 Q2 |
| ProShare Advisors LLC | 89.8k | 0.36% | $6.6M | added +7.3% | 2017 Q4 |
| Public Sector Pension Investment Board | 88.7k | 0.36% | $6.5M | added +3.5% | 2015 Q3 |
| Mutual OF America Capital Management LLC | 87.5k | 0.35% | $6.4M | trimmed -0.5% | 2018 Q2 |
| Trexquant Investment LP | 78.4k | 0.32% | $5.7M | added +70.1% | 2022 Q4 |
| Numerai GP LLC | 76.6k | 0.31% | $5.6M | trimmed -22% | 2025 Q2 |
| Russell Investments Group, LTD. | 71.6k | 0.29% | $5.2M | added +515.8% | 2016 Q4 |
| Rhumbline Advisers | 71.2k | 0.29% | $5.2M | added +1.4% | ≤2013 |
| Leeward Investments, LLC - MA | 69.8k | 0.28% | $5.1M | trimmed -2.6% | 2022 Q1 |
| Deprince Race & Zollo INC | 68.0k | 0.27% | $5.0M | opened | 2026 Q1 |
| Engineers Gate Manager LP | 64.7k | 0.26% | $4.7M | added +29.7% | 2022 Q4 |
Largest 50 of 255 shown; the full ranked, searchable register is at boothcheck.com/holders/IOSP. Related filers are grouped using the filings' own included-manager declarations. Historically, several managers opening new positions in the same quarter said almost nothing about the quarter that followed (59,118 cases since 2013). A filed record, not a forecast. Nothing here is investment advice.