Western Digital Corporation
CH ˙ BRSE ˙ US9581021055
DETTE SYMBOL ER IKKE LÆNGERE AKTIVT
SecurityCH:12355 / Western Digital Corporation
InstitutionRhumbline Advisers
Latest Disclosed Ownership594,405 shares
Latest Disclosed Value $ 160,780,480
Rhumbline Advisers reports 6.40% decrease in ownership of 12355 / Western Digital Corporation

On May 12, 2026 - Rhumbline Advisers filed a 13F-HR form disclosing ownership of 594,405 shares of Western Digital Corporation (CH:12355) valued at $160,780,480 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 13, 2026 disclosing 635,036 shares of Western Digital Corporation. This represents a change in shares of -6.40% 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)
2026-05-12 2026-03-31 13F WESTN DIGITAL CORP COM COM 958102105 594,405 -40,631 -6.40 160,780 46.97 0.1375
2026-02-13 2025-12-31 13F WESTN DIGITAL CORP COM COM 958102105 635,036 -33,676 -5.04 109,398 36.26 0.0884
2025-11-06 2025-09-30 13F WESTN DIGITAL CORP COM COM 958102105 668,712 -11,589 -1.70 80,285 84.43 0.0645
2025-08-12 2025-06-30 13F WESTN DIGITAL CORP COM COM 958102105 680,301 5,427 0.80 43,532 59.55 0.0373
2025-05-29 2025-03-31 13F/A-1 WESTN DIGITAL CORP COM COM 958102105 674,874 46,202 7.35 27,285 -27.21 0.0255
2025-04-08 2025-03-31 13F WESTN DIGITAL CORP COM COM 958102105 674,874 46,202 27,285 0.0255
2025-05-29 2024-12-31 13F/A-1 WESTN DIGITAL CORP COM COM 958102105 628,672 8,029 1.29 37,488 -11.55 0.0335
2025-01-30 2024-12-31 13F WESTN DIGITAL CORP COM COM 958102105 628,672 8,029 37,488 0.0335
2024-11-12 2024-09-30 13F WESTN DIGITAL CORP COM COM 958102105 620,643 -6,990 -1.11 42,384 -10.88 0.0382
2024-08-01 2024-06-30 13F WESTN DIGITAL CORP COM COM 958102105 627,633 31,145 5.22 47,556 16.83 0.0447
2024-05-09 2024-03-31 13F WESTN DIGITAL CORP COM COM 958102105 596,488 -25,161 -4.05 40,704 25.03 0.0391
2024-02-08 2023-12-31 13F WESTN DIGITAL CORP COM COM 958102105 621,649 14,040 2.31 32,556 17.42 0.0341
2023-11-09 2023-09-30 13F WESTN DIGITAL CORP COM COM 958102105 607,609 -7,338 -1.19 27,725 18.87 0.0322
2023-08-08 2023-06-30 13F WESTN DIGITAL CORP COM COM 958102105 614,947 874 0.14 23,325 101,308.70 0.0261
2023-05-11 2023-03-31 13F WESTN DIGITAL CORP COM COM 958102105 614,073 -2,660 -0.43 23 -99.88 0.0285
2023-02-14 2022-12-31 13F WESTN DIGITAL CORP COM COM 958102105 616,733 31,128 5.32 19,458 2.08 0.0262
2022-11-10 2022-09-30 13F WESTN DIGITAL CORP COM COM 958102105 585,605 27,442 4.92 19,061 -23.82 0.0284
2022-08-11 2022-06-30 13F WESTN DIGITAL CORP COM COM 958102105 558,163 61,586 12.40 25,022 1.49 0.0365
2022-05-12 2022-03-31 13F WESTN DIGITAL CORP COM COM 958102105 496,577 7,339 1.50 24,655 -22.72 0.0317
2022-02-10 2021-12-31 13F WESTN DIGITAL CORP COM COM 958102105 489,238 4,193 0.86 31,903 16.54 0.0391
2021-11-12 2021-09-30 13F WESTN DIGITAL CORP COM COM 958102105 485,045 -13,448 -2.70 27,376 -22.84 0.0371
2021-08-05 2021-06-30 13F WESTN DIGITAL CORP COM COM 958102105 498,493 -8,493 -1.68 35,478 4.84 0.0466
2021-05-06 2021-03-31 13F WESTN DIGITAL CORP COM COM 958102105 506,986 -91,319 -15.26 33,841 2.12 0.0460
2021-02-10 2020-12-31 13F WESTN DIGITAL CORP COM COM 958102105 598,305 21,253 3.68 33,140 57.13 0.0457
2020-11-12 2020-09-30 13F WESTN DIGITAL CORP COM COM 958102105 577,052 48,210 9.12 21,091 -9.67 0.0330
2020-08-13 2020-06-30 13F WESTN DIGITAL CORP COM COM 958102105 528,842 -27,889 -5.01 23,348 0.76 0.0390
2020-05-06 2020-03-31 13F WESTN DIGITAL CORP COM COM 958102105 556,731 32,731 6.25 23,171 -30.33 0.0486
2020-02-05 2019-12-31 13F WESTN DIGITAL CORP COM COM 958102105 524,000 41,556 8.61 33,258 15.59 0.0556
2019-10-23 2019-09-30 13F WESTN DIGITAL CORP COM COM 958102105 482,444 8,629 1.82 28,773 27.71 0.0526
2019-08-14 2019-06-30 13F WESTN DIGITAL CORP COM COM 958102105 473,815 43,243 10.04 22,530 8.88 0.0423
2019-05-01 2019-03-31 13F WESTN DIGITAL CORP COM COM 958102105 430,572 -59,158 -12.08 20,693 14.29 0.0401
2019-01-31 2018-12-31 13F WESTN DIGITAL CORP COM COM 958102105 489,730 -2,463 -0.50 18,105 -37.16 0.0394
2018-11-07 2018-09-30 13F WESTN DIGITAL CORP COM COM 958102105 492,193 -10,976 -2.18 28,813 -26.03 0.0556
2018-08-06 2018-06-30 13F WESTN DIGITAL CORP COM COM 958102105 503,169 -28,033 -5.28 38,950 -20.53 0.0786
2018-05-02 2018-03-31 13F WESTN DIGITAL CORP COM COM 958102105 531,202 1,977 0.37 49,014 16.45 0.1024
2018-02-09 2017-12-31 13F WESTN DIGITAL CORP COM COM 958102105 529,225 11,721 2.26 42,089 -5.87 0.0855
2017-11-06 2017-09-30 13F WESTN DIGITAL CORP COM COM 958102105 517,504 7,255 1.42 44,712 -1.10 0.0972
2017-08-02 2017-06-30 13F WESTN DIGITAL CORP COM COM 958102105 510,249 27,386 5.67 45,208 13.44 0.1032
2017-05-02 2017-03-31 13F WESTN DIGITAL CORP COM COM 958102105 482,863 10,363 2.19 39,851 24.12 0.0931
2017-01-27 2016-12-31 13F WESTN DIGITAL CORP COM COM 958102105 472,500 44,714 10.45 32,106 28.36 0.0814
2016-11-08 2016-09-30 13F WESTN DIGITAL CORP COM COM 958102105 427,786 18,156 4.43 25,013 29.21 0.0689
2016-08-11 2016-06-30 13F WESTN DIGITAL CORP COM COM 958102105 409,630 104,760 34.36 19,359 34.42 0.0574
2016-05-02 2016-03-31 13F WESTERN DIGITAL CORP COMMON ST COM 958102105 304,870 10,691 3.63 14,402 -18.47 0.0447
2016-02-03 2015-12-31 13F WESTERN DIGITAL CORP COMMON ST COM 958102105 294,179 2,780 0.95 17,665 -23.69 0.0568
2015-11-04 2015-09-30 13F WESTERN DIGITAL CORP COMMON ST COM 958102105 291,399 8,480 3.00 23,149 4.34 0.0788
2015-08-04 2015-06-30 13F WESTERN DIGITAL CORP COMMON ST COM 958102105 282,919 6,778 2.45 22,187 -11.72 0.0707
2015-05-12 2015-03-31 13F WESTERN DIGITAL CORP COMMON ST COM 958102105 276,141 -5,014 -1.78 25,132 -19.25 0.0725
2015-02-06 2014-12-31 13F WESTERN DIGITAL CORP COMMON ST COM 958102105 281,155 -712 -0.25 31,124 13.46 0.0904
2014-11-12 2014-09-30 13F WESTERN DIGITAL CORP COMMON ST COM 958102105 281,867 2,734 0.98 27,431 6.47 0.0824
2014-08-06 2014-06-30 13F WESTERN DIGITAL CORP COMMON ST COM 958102105 279,133 -7,034 -2.46 25,764 -1.95 0.0756
2014-05-06 2014-03-31 13F WESTERN DIGITAL CORP COMMON ST COM 958102105 286,167 -6,880 -2.35 26,276 6.87 0.0779
2014-02-03 2013-12-31 13F WESTERN DIGITAL CORP COMMON ST COM 958102105 293,047 -17,867 -5.75 24,587 24.73 0.0725
2013-11-05 2013-09-30 13F WESTERN DIGITAL CORP COMMON ST COM 958102105 310,914 6,507 2.14 19,712 4.29 0.0611
2013-08-07 2013-06-30 13F WESTERN DIGITAL CORP COMMON ST COM 958102105 304,407 304,407 18,901 0.0607
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.