Iron Mountain Incorporated
MX ˙ BMV ˙ US46284V1017
SecurityMX:IRM1 / Iron Mountain Incorporated
InstitutionMadison Asset Management, LLC
Latest Disclosed Ownership17,052 shares
Latest Disclosed Value $ 1,741,691
Madison Asset Management, LLC ownership in IRM1 / Iron Mountain Incorporated

On May 7, 2026 - Madison Asset Management, LLC filed a 13F-HR form disclosing ownership of 17,052 shares of Iron Mountain Incorporated (MX:IRM1) valued at $1,741,691 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 4, 2026 disclosing 17,052 shares of Iron Mountain Incorporated. This represents a change in shares of 0.00% during the quarter.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date		 Effective
Date		Form Security Class ID Avg Price
Paid (Est)		 Reported
Shares		 ΔShares ΔShares
(%)		 Reported
Value
(x1000)		 ΔValue
(%)		 Alloc
(%)		 ΔAlloc ΔAlloc (%) Cost Basis
(x1000)		 Unrealized
Gain/Loss
(x1000)
2026-05-07 2026-03-31 13F Iron Mountain COM 46284V101 17,052 0 0.00 1,742 23.13 0.0216
2026-02-04 2025-12-31 13F Iron Mountain COM 46284V101 17,052 -908 -5.06 1,414 -22.73 0.0163
2025-11-06 2025-09-30 13F Iron Mountain COM 46284V101 17,960 -571 -3.08 1,831 -3.68 0.0202
2025-08-11 2025-06-30 13F Iron Mountain COM 46284V101 18,531 0 0.00 1,901 19.20 0.0205
2025-05-06 2025-03-31 13F Iron Mountain COM 46284V101 18,531 -5,838 -23.96 1,594 -37.76 0.0178
2025-02-10 2024-12-31 13F Iron Mountain COM 46284V101 24,369 0 0.00 2,561 -11.54 0.0289
2024-11-12 2024-09-30 13F Iron Mountain COM 46284V101 24,369 -5,714 -18.99 2,896 7.38 0.0326
2024-08-09 2024-06-30 13F Iron Mountain COM 46284V101 30,083 0 0.00 2,696 11.77 0.0334
2024-05-09 2024-03-31 13F Iron Mountain COM 46284V101 30,083 0 0.00 2,413 14.58 0.0297
2024-02-12 2023-12-31 13F Iron Mountain COM 46284V101 30,083 -319 -1.05 2,105 16.49 0.0285
2023-11-13 2023-09-30 13F Iron Mountain COM 46284V101 30,402 -71 -0.23 1,807 4.39 0.0265
2023-08-01 2023-06-30 13F Iron Mountain COM 46284V101 30,473 0 0.00 1,731 7.38 0.0253
2023-04-26 2023-03-31 13F Iron Mountain COM 46284V101 30,473 -4,398 -12.61 1,612 161,100.00 0.0245
2023-02-08 2022-12-31 13F Iron Mountain COM 46284V101 34,871 -728 -2.05 2 -99.94 0.0273
2022-11-10 2022-09-30 13F Iron Mountain COM 46284V101 35,599 -139 -0.39 1,565 -10.06 0.0264
2022-08-09 2022-06-30 13F Iron Mountain COM 46284V101 35,738 -440 -1.22 1,740 -13.22 0.0272
2022-05-12 2022-03-31 13F Iron Mountain COM 46284V101 36,178 18 0.05 2,005 5.97 0.0287
2022-02-15 2021-12-31 13F Iron Mountain COM 46284V101 36,160 2,538 7.55 1,892 29.50 0.0248
2021-11-12 2021-09-30 13F Iron Mountain COM 46284V101 33,622 1,400 4.34 1,461 7.11 0.0201
2021-08-09 2021-06-30 13F Iron Mountain COM 46284V101 32,222 1,226 3.96 1,364 18.92 0.0184
2021-05-11 2021-03-31 13F Iron Mountain COM 46284V101 30,996 913 3.03 1,147 29.31 0.0160
2021-02-12 2020-12-31 13F Iron Mountain COM 46284V101 30,083 0 0.00 887 10.05 0.0130
2020-11-12 2020-09-30 13F Iron Mountain COM 46284V101 30,083 0 0.00 806 2.68 0.0135
2020-08-13 2020-06-30 13F Iron Mountain COM 46284V101 30,083 9,000 42.69 785 56.37 0.0138
2020-05-12 2020-03-31 13F Iron Mountain COM 46284V101 21,083 7,600 56.37 502 16.74 0.0103
2020-02-12 2019-12-31 13F Iron Mountain COM 46284V101 13,483 13,483 430 0.0066
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.