Mariner
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Mariner’s White Mountains Insurance WTM Stock Holding History

Mariner’s Portfolio WTM Stock Details WTM Fund Activity
Bought
Maintained
Sold
Quarter Market Value Status Shares Change in
Stake 		Trade Value Portfolio Weight Portfolio Position
2026
Q1 		$1.33M Buy
607
+205
+51% +$439K ﹤0.01% 1763
2025
Q4 		$835K Buy
402
+188
+88% +$368K ﹤0.01% 2074
2025
Q3 		$357K Sell
214
-528
-71% -$942K ﹤0.01% 2677
2025
Q2 		$1.33M Buy
742
+22
+3% +$39.1K ﹤0.01% 1613
2025
Q1 		$1.39M Sell
720
-105
-13% -$198K ﹤0.01% 1459
2024
Q4 		$1.6M Buy
825
+151
+22% +$285K ﹤0.01% 1342
2024
Q3 		$1.14M Buy
674
+74
+12% +$129K ﹤0.01% 1505
2024
Q2 		$1.09M Buy
600
+117
+24% +$207K ﹤0.01% 1446
2024
Q1 		$867K Buy
483
+91
+23% +$153K ﹤0.01% 1615
2023
Q4 		$590K Sell
392
-30
-7% -$44.6K ﹤0.01% 1839
2023
Q3 		$631K Buy
422
+79
+23% +$121K ﹤0.01% 1615
2023
Q2 		$476K Sell
343
-4
-1% -$5.63K ﹤0.01% 1781
2023
Q1 		$478K Buy
347
+7
+2% +$10K ﹤0.01% 1726
2022
Q4 		$481K Buy
340
+26
+8% +$35.2K ﹤0.01% 1674
2022
Q3 		$409K Buy
+314
New +$406K ﹤0.01% 1545
2018
Q4 		– Sell
-479
Closed -$448K – 900
2018
Q3 		$448K Sell
479
-834
-64% -$773K 0.01% 580
2018
Q2 		$1.19M Buy
+1,313
New +$1.16M 0.03% 368

Other funds holding WTM

Dimensional Fund Advisors
Dimensional Fund Advisors Austin, Texas $481B AUM 30.42% 1-Year Est. Return
Neuberger Berman Group
Neuberger Berman Group New York $131B AUM 28.36% 1-Year Est. Return
RRAM
River Road Asset Management Louisville, Kentucky $8.99B AUM 12.83% 1-Year Est. Return
VPM
Vanguard Portfolio Management Malvern, Pennsylvania $1.91T AUM
BlackRock
BlackRock New York $5.72T AUM 30.48% 1-Year Est. Return
VCM
Vanguard Capital Management Malvern, Pennsylvania $4.04T AUM
CB
Cooke & Bieler Philadelphia, Pennsylvania $8.84B AUM 6.92% 1-Year Est. Return
Fuller & Thaler Asset Management
Fuller & Thaler Asset Management San Mateo, California $29.7B AUM 43.33% 1-Year Est. Return
FMI
Fiduciary Management Inc Milwaukee, Wisconsin $8.06B AUM 6.78% 1-Year Est. Return
WCM
Wallace Capital Management Dallas, Texas $871M AUM 13.69% 1-Year Est. Return

Mariner's WTM Position: Q1 2026 in Review

Mariner increased its White Mountains Insurance (WTM) stake by 51% in Q1 2026, buying an estimated $439K and bringing the position to 607 shares worth $1.33M. The position accounts for ﹤0.01% of the portfolio, ranked #1763.

Mariner first reported a position in WTM in Q2 2018 and has held it in 17 quarters since. The position peaked at $1.6M in Q4 2024. 367 funds tracked by Wall St. Rank hold WTM as of Q1 2026.

  • Mariner held 607 shares of White Mountains Insurance worth $1.33M as of Q1 2026.
  • Mariner bought 205 White Mountains Insurance shares in Q1 2026, an estimated $439K.
  • White Mountains Insurance made up ﹤0.01% of Mariner's portfolio in Q1 2026, its #1763 holding.
  • Mariner first reported a position in White Mountains Insurance in Q2 2018 and has held it in 17 quarters since.
  • Mariner's White Mountains Insurance position peaked at $1.6M in Q4 2024.
  • 367 funds tracked by Wall St. Rank held White Mountains Insurance as of Q1 2026.

Based on Mariner's 13F filing for Q1 2026, filed 13 May 2026.