William Blair & Company
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William Blair & Company’s iShares MBS ETF MBB Stock Holding History

William Blair & Company’s Portfolio MBB Stock Details MBB Fund Activity
Bought
Maintained
Sold
Quarter Market Value Status Shares Change in
Stake 		Trade Value Portfolio Weight Portfolio Position
2026
Q1 		$531K Sell
5,593
-207
-4% -$19.8K ﹤0.01% 1127
2025
Q4 		$552K Sell
5,800
-39
-0.7% -$3.72K ﹤0.01% 1110
2025
Q3 		$556K Buy
5,839
+1,059
+22% +$99.5K ﹤0.01% 1081
2025
Q2 		$449K Sell
4,780
-2,010
-30% -$186K ﹤0.01% 1121
2025
Q1 		$637K Sell
6,790
-809
-11% -$74.8K ﹤0.01% 1019
2024
Q4 		$697K Sell
7,599
-411
-5% -$38.3K ﹤0.01% 999
2024
Q3 		$767K Buy
8,010
+751
+10% +$71K ﹤0.01% 985
2024
Q2 		$666K Buy
7,259
+560
+8% +$51K ﹤0.01% 1006
2024
Q1 		$619K Buy
6,699
+3,987
+147% +$369K ﹤0.01% 1032
2023
Q4 		$255K Sell
2,712
-497
-15% -$44.6K ﹤0.01% 1314
2023
Q3 		$285K Sell
3,209
-100
-3% -$9.14K ﹤0.01% 1258
2023
Q2 		$309K Sell
3,309
-358
-10% -$33.7K ﹤0.01% 1242
2023
Q1 		$347K Sell
3,667
-126
-3% -$11.9K ﹤0.01% 1174
2022
Q4 		$352K Sell
3,793
-638
-14% -$58.8K ﹤0.01% 1158
2022
Q3 		$406K Buy
4,431
+264
+6% +$25.6K ﹤0.01% 1114
2022
Q2 		$406K Buy
4,167
+582
+16% +$57.1K ﹤0.01% 1142
2022
Q1 		$365K Sell
3,585
-2,564
-42% -$268K ﹤0.01% 1284
2021
Q4 		$661K Buy
6,149
+921
+18% +$99.1K ﹤0.01% 1106
2021
Q3 		$565K Sell
5,228
-3,891
-43% -$422K ﹤0.01% 1114
2021
Q2 		$987K Sell
9,119
-3,986
-30% -$432K ﹤0.01% 924
2021
Q1 		$1.42M Buy
13,105
+1,935
+17% +$212K 0.01% 786
2020
Q4 		$1.23M Sell
11,170
-19
-0.2% -$2.09K ﹤0.01% 788
2020
Q3 		$1.24M Buy
11,189
+6,106
+120% +$675K 0.01% 696
2020
Q2 		$563K Buy
5,083
+1,937
+62% +$214K ﹤0.01% 901
2020
Q1 		$347K Buy
3,146
+1,299
+70% +$141K ﹤0.01% 974
2019
Q4 		$200K Sell
1,847
-764
-29% -$82.5K ﹤0.01% 1308
2019
Q3 		$283K Buy
2,611
+580
+29% +$62.6K ﹤0.01% 1145
2019
Q2 		$219K Hold
2,031
– – ﹤0.01% 1268
2019
Q1 		$216K Sell
2,031
-500
-20% -$52.6K ﹤0.01% 1273
2018
Q4 		$265K Sell
2,531
-134
-5% -$13.8K ﹤0.01% 1130
2018
Q3 		$275K Sell
2,665
-867
-25% -$90K ﹤0.01% 1178
2018
Q2 		$368K Sell
3,532
-1,407
-28% -$146K ﹤0.01% 1040
2018
Q1 		$517K Sell
4,939
-13,177
-73% -$1.38M ﹤0.01% 913
2017
Q4 		$1.93M Sell
18,116
-993
-5% -$106K 0.01% 581
2017
Q3 		$2.05M Buy
19,109
+3,862
+25% +$414K 0.02% 552
2017
Q2 		$1.63M Buy
15,247
+11,540
+311% +$1.23M 0.01% 621
2017
Q1 		$396K Sell
3,707
-326
-8% -$34.6K ﹤0.01% 980
2016
Q4 		$429K Sell
4,033
-167
-4% -$18.1K ﹤0.01% 881
2016
Q3 		$462K Sell
4,200
-597
-12% -$65.6K ﹤0.01% 858
2016
Q2 		$527K Buy
+4,797
New +$525K ﹤0.01% 787
2014
Q2 		– Sell
-829,100
Closed -$88M – 2101
2014
Q1 		$88M Buy
829,100
+239,450
+41% +$25.4M 0.15% 209
2013
Q4 		$61.7M Buy
589,650
+99,422
+20% +$10.5M 0.1% 298
2013
Q3 		$51.9M Buy
490,228
+262,228
+115% +$27.4M 0.09% 318
2013
Q2 		$24M Buy
+228,000
New +$24.4M 0.05% 450

Other funds holding MBB

Bank of America
Bank of America Charlotte, North Carolina $1.37T AUM 24.88% 1-Year Est. Return
JP Morgan Chase
JP Morgan Chase New York $1.56T AUM 27.86% 1-Year Est. Return
Envestnet Asset Management
Envestnet Asset Management Chicago, Illinois $374B AUM 17.66% 1-Year Est. Return
LPL Financial
LPL Financial San Diego, California $377B AUM 19.32% 1-Year Est. Return
UBS Group
UBS Group Zurich, Switzerland $666B AUM 30.12% 1-Year Est. Return
TWIM
TIAA Wealth Investment Management New York $13.1B AUM
Ameriprise
Ameriprise Minneapolis, Minnesota $432B AUM 30.22% 1-Year Est. Return
Morgan Stanley
Morgan Stanley New York $1.66T AUM 25.57% 1-Year Est. Return
TCIIS
TIAA-CREF Individual & Institutional Services New York $26B AUM
Truist Financial
Truist Financial Charlotte, North Carolina $74.2B AUM 21.09% 1-Year Est. Return

William Blair & Company's MBB Position: Q1 2026 in Review

William Blair & Company reduced its iShares MBS ETF (MBB) stake by 3.6% in Q1 2026, selling an estimated $19.8K and leaving 5,593 shares worth $531K. The position accounts for ﹤0.01% of the portfolio, ranked #1127.

William Blair & Company first reported a position in MBB in Q2 2013 and has held it in 44 quarters since. The position peaked at $88M in Q1 2014. 1,019 funds tracked by Wall St. Rank hold MBB as of Q1 2026.

  • William Blair & Company held 5,593 shares of iShares MBS ETF worth $531K as of Q1 2026.
  • William Blair & Company sold 207 iShares MBS ETF shares in Q1 2026, an estimated $19.8K.
  • iShares MBS ETF made up ﹤0.01% of William Blair & Company's portfolio in Q1 2026, its #1127 holding.
  • William Blair & Company first reported a position in iShares MBS ETF in Q2 2013 and has held it in 44 quarters since.
  • William Blair & Company's iShares MBS ETF position peaked at $88M in Q1 2014.
  • 1,019 funds tracked by Wall St. Rank held iShares MBS ETF as of Q1 2026.

Based on William Blair & Company's 13F filing for Q1 2026, filed 8 May 2026.