% of shares outstanding not shown: no SEC cover-page share count falls within 120 days of the 2026-Q1 quarter end, so any percentage would rest on a count that cannot speak for this quarter. Holder share counts are shown as filed.
Crowding percentile withheld — no market cap for MAIN in the served universe — the cohort is size-matched, and an unmatched percentile would compare a micro-cap register to a mega-cap one.
Rows rank by the value each filer reported — 13F filers price their own positions, so a holder with fewer shares can rank just above one with more.
| Holder | 2024-Q4 | 2025-Q1 | 2025-Q2 | 2025-Q3 | 2025-Q4 | 2026-Q1 | Latest value |
|---|---|---|---|---|---|---|---|
| PRICE T ROWE ASSOCIATES INC /MD/ | 3.4M | 3.2M | 3.5M | 2.6M | 2.7M | 2.7M | $143M |
| VAN ECK ASSOCIATES CORP | 1.3M | 1.2M | 1.2M | 2.4M | 1.1M | 2.1M | $112M |
| UBS Group AG | 94K | 244K | 333K | 867K | 612K | 1.3M | $71M |
| MORGAN STANLEY | 971K | 968K | 1.0M | 986K | 868K | 855K | $45M |
| Legal & General Group Plc | 624K | 651K | 675K | 625K | 720K | 784K | $42M |
| D. E. Shaw & Co., Inc. | — | 8K | 74K | 102K | 279K | 543K | $29M |
| TWO SIGMA INVESTMENTS, LP | 38K | 175K | 161K | 129K | 72K | 524K | $28M |
| Qube Research & Technologies Ltd | — | 114K | 164K | 59K | 190K | 486K | $26M |
| Muzinich & Co., Inc. | 223K | 247K | 317K | 367K | 440K | 485K | $26M |
| ADELL HARRIMAN & CARPENTER INC | 426K | 448K | 454K | 454K | 478K | 485K | $26M |
| Invesco Ltd. | 139K | 532K | 507K | 445K | 420K | 432K | $23M |
| BlackRock, Inc. | 459K | 456K | 586K | 218K | 210K | 424K | $22M |
| Sumitomo Mitsui Trust Group, Inc. | 221K | 243K | 287K | 335K | 356K | 371K | $20M |
| MILLENNIUM MANAGEMENT LLC | — | 19K | 14K | 46K | 247K | 360K | $19M |
| LPL Financial LLC | 299K | 307K | 342K | 382K | 348K | 348K | $18M |
Shares reported each quarter by the largest current holders. Green = added vs the prior filing, red = trimmed, grey = roughly held; a dash is a quarter with no 13F on file (a gap is skipped, not read as an exit). 13F is filed up to 45 days after quarter-end. Up to 40 quarters (10 years) available — use the selector above.
Holder count only — too few computable %-of-shares-outstanding quarters for a % pane. Line breaks are quarters with no 13F record, never interpolated.
Short interest has its own tab now — open SI →
Source: SEC Form 13F — every institution manager (≥ $100M in 13F securities) reporting a long US-listed position, across ~10,250 filers over 10 years of history. 13F is long-only, US-listed, filed up to 45 days after quarter-end.
| Biggest buyers | Δ shares | Δ value | |
|---|---|---|---|
| VAN ECK ASSOCIATES CORP | +976,576 | $52M | ADD |
| UBS Group AG | +726,936 | $38M | ADD |
| TWO SIGMA INVESTMENTS, LP | +451,631 | $24M | ADD |
| Qube Research & Technologies Ltd | +295,904 | $16M | ADD |
| D. E. Shaw & Co., Inc. | +264,791 | $14M | ADD |
| Biggest sellers | Δ shares | Δ value | |
|---|---|---|---|
| Corient Private Wealth LLC | −1,765,523 | $94M | TRIM |
| JANE STREET GROUP, LLC | −314,648 | $17M | CLOSE |
| Sound Income Strategies, LLC | −217,879 | $12M | TRIM |
| TUDOR INVESTMENT CORP ET AL | −165,934 | $9M | TRIM |
| HRT FINANCIAL LP | −105,983 | $6M | CLOSE |
The 2025-Q4 register is as-filed in ITS OWN share basis; every count below was rebased into the 2026-Q1 basis (no split in between, factor 1). Dollar figures value the SHARE delta at one price — the 2026-03-31 close — rather than differencing two filings' own reported values, which would mix the quarter's price move into the trade figure.
13Fs disclose LONG US-listed positions only — shorts, most derivatives, bonds and non-US listings are invisible here, and a filer's quarter-over-quarter change is not necessarily a trade (index rebalances, in-kind transfers and entity successions all read as flow).
| Quarter | Holders | Shares held | % shares out | Value held |
|---|---|---|---|---|
| 2026-Q1 | 422 | 23,228,180 | — | $1.2B |
| 2025-Q4 | 429 | 21,632,374 | — | $1.3B |
| 2025-Q3 | 406 | 20,449,566 | — | $1.3B |
| 2025-Q2 | 404 | 19,997,826 | — | $1.3B |
| 2025-Q1 | 391 | 18,891,219 | — | $1.1B |
| 2024-Q4 | 401 | 18,890,295 | — | $1.1B |
| 2024-Q3 | 353 | 18,675,937 | — | $935M |
| 2024-Q2 | 339 | 17,382,741 | — | $876M |
| 2024-Q1 | 323 | 18,823,995 | — | $887M |
| 2023-Q4 | 312 | 18,351,984 | — | $791M |
| 2023-Q3 | 291 | 17,630,072 | — | $716M |
| 2023-Q2 | 288 | 16,509,048 | — | $660M |
| 2023-Q1 | 271 | 15,640,273 | — | $617M |
| 2022-Q4 | 271 | 15,512,206 | — | $571M |
| 2022-Q3 | 247 | 14,553,600 | — | $490M |
| 2022-Q2 | 243 | 13,748,946 | — | $529M |
| 2022-Q1 | 256 | 12,931,396 | — | $551M |
| 2021-Q4 | 256 | 12,393,627 | — | $556M |
| 2021-Q3 | 235 | 12,270,136 | — | $506M |
| 2021-Q2 | 227 | 11,802,337 | — | $485M |
| 2021-Q1 | 229 | 12,975,622 | — | $509M |
| 2020-Q4 | 210 | 14,532,065 | — | $469M |
| 2020-Q3 | 199 | 13,262,574 | — | $392M |
| 2020-Q2 | 207 | 12,852,267 | — | $400M |
| 2020-Q1 | 220 | 14,303,929 | — | $282M |
| 2019-Q4 | 252 | 14,869,941 | — | $638M |
| 2019-Q3 | 230 | 14,490,245 | — | $626M |
| 2019-Q2 | 223 | 16,230,457 | — | $668M |
| 2019-Q1 | 221 | 14,159,201 | — | $526M |
| 2018-Q4 | 219 | 14,418,059 | — | $488M |
| 2018-Q3 | 215 | 14,556,279 | — | $579M |
| 2018-Q2 | 204 | 14,639,666 | — | $556M |
| 2018-Q1 | 207 | 15,197,127 | — | $560M |
| 2017-Q4 | 205 | 16,290,225 | — | $646M |
| 2017-Q3 | 180 | 15,714,416 | — | $624M |
| 2017-Q2 | 177 | 14,999,747 | — | $582M |
| 2017-Q1 | 178 | 15,207,808 | — | $582M |
| 2016-Q4 | 172 | 14,102,116 | — | $518M |
| 2016-Q3 | 149 | 13,992,169 | — | $480M |
| 2016-Q2 | 147 | 15,088,368 | — | $495M |
| 2016-Q1 | 141 | 14,467,694 | — | $453M |
| 2015-Q4 | 136 | 15,058,065 | — | $438M |
| 2015-Q3 | 126 | 14,344,622 | — | $385M |
| 2015-Q2 | 132 | 13,187,495 | — | $421M |
| 2015-Q1 | 131 | 13,275,837 | — | $415M |
| 2014-Q4 | 134 | 11,506,541 | — | $397M |
| 2014-Q3 | 124 | 11,350,173 | — | $352M |
| 2014-Q2 | 134 | 11,723,846 | — | $391M |
| 2014-Q1 | 129 | 12,017,191 | — | $399M |
| 2013-Q4 | 125 | 11,327,878 | — | $377M |
| 2013-Q3 | 118 | 10,789,836 | — | $328M |
| 2013-Q2 | 113 | 8,217,853 | — | $233M |
| 2013-Q1 | 9 | 202,739 | — | $6M |
