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Funds (13F)

William Blair Investment Management, LLC

Backtest from 13 Nov 2015 to 2 Nov 2026 · weekly · hypothetical

Watch this strategy
Return a year
+13.0%
S&P 500 +14.6%
Last 12 months
+6.0%
S&P 500 +12.1%
Sharpe ratio
0.59
S&P 500 0.76
Biggest drop
−36.1%
S&P 500 −31.8%
$10.0k$20.0k$40.0k 201520172019202120232025 $44.7k$38.3k
StrategyS&P 500 $10,000 in William Blair Investment Management, LLC from 13 Nov 2015 against the S&P 500 (total return) over the same dates, marked weekly, log scale. Hypothetical: before taxes and trading costs.

About

Copies William Blair Investment Management, LLC's quarterly 13F holdings in the companies we cover, weighted by reported value: it buys on the first trading day after each 13F is filed (up to 45 days after the quarter) and holds until the next filing. A 13F shows long US-listed positions only, at the quarter's end, so this misses shorts, cash, bonds, non-US holdings and trading within the quarter.

William Blair Investment Management, LLC's 13F holdings →

Key statistics

MeasureStrategyS&P 500
Return a year (compound)+13.0%+14.6%
Total return+283%+347%
Last 12 months+6.0%+12.1%
Last 3 months−2.0%—
Last month−5.1%—
This year so far+5.6%—
Volatility a year19.9%16.7%
Sharpe ratio0.590.76
Biggest drop−36.1%−31.8%
Beta to the S&P 5001.131.00
Alpha a year (t-statistic)−2.4% (−1.23)—
Share of weeks up58%—

Sharpe ratio uses returns above the 3-month Treasury bill rate. Alpha is the yearly return left after allowing for the strategy's exposure to the S&P 500 (CAPM); a t-statistic below about 2 means it cannot be told apart from luck.

Insights

CompanyWeightHeld sinceReturn since
TSM7.3%——
NVDA5.3%——
GOOGL3.5%——
AAPL2.9%——
AVGO2.4%——
MSFT2.4%——
META1.7%——
AMZN1.5%——
MA1.5%——
AMD1.4%——
AMAT1.1%——
GE0.9%——
AZN0.9%——
PRMB0.9%——
P0.8%——
APH0.8%——
LIN0.8%——
ONTO0.8%——
BWA0.8%——
CG0.8%——
ARGX0.8%——
MLI0.8%——
MNST0.8%——
FFIV0.8%——
CW0.8%——
SNOW0.7%——
TWST0.7%——
TEVA0.7%——
UNH0.7%——
CRWD0.7%——
RRX0.7%——
KRYS0.7%——
CRS0.6%——
POWI0.6%——
NVT0.6%——
GH0.6%——
HALO0.6%——
TLN0.6%——
TRU0.6%——
CCJ0.6%——
STRL0.6%——
COST0.6%——
ALHC0.6%——
CHRW0.6%——
STX0.6%——
DIOD0.6%——
BWXT0.6%——
AKAM0.6%——
BWIN0.6%——
BSY0.6%——
LSCC0.6%——
MDGL0.5%——
EG0.5%——
A0.5%——
ORLY0.5%——
DT0.5%——
MIRM0.5%——
HQY0.5%——
IDXX0.5%——
NOW0.5%——
SYNA0.5%——
TXN0.5%——
SN0.5%——
WST0.5%——
LOPE0.5%——
LFUS0.5%——
CNQ0.5%——
RS0.4%——
FPS0.4%——
PTCT0.4%——
TKR0.4%——
CYTK0.4%——
LECO0.4%——
EXP0.4%——
CLH0.4%——
NOVT0.4%——
BIRK0.4%——
FHN0.4%——
ETSY0.4%——
TIGO0.4%——
DBD0.4%——
GTX0.4%——
EHC0.4%——
APPF0.4%——
MAR0.3%——
NBHC0.3%——
CMG0.3%——
SAIA0.3%——
RGEN0.3%——
FRPT0.3%——
JAZZ0.3%——
MLM0.3%——
KNX0.3%——
WFRD0.3%——
GMED0.3%——
NU0.3%——
HBM0.3%——
ONB0.3%——
LB0.3%——
WGS0.3%——
CASY0.3%——
MANH0.3%——
GKOS0.3%——
CHDN0.3%——
EYE0.3%——
CAVA0.3%——
CFR0.3%——
CPRT0.3%——
VCEL0.3%——
CART0.3%——
FLS0.3%——
VCYT0.3%——
OSIS0.3%——
EVR0.3%——
NXT0.3%——
STEP0.3%——
VSH0.3%——
MMSI0.3%——
VRSK0.2%——
GWRE0.2%——
AAOI0.2%——
HLIO0.2%——
LRN0.2%——
PWP0.2%——
APG0.2%——
KMT0.2%——
JBTM0.2%——
INSM0.2%——
LAUR0.2%——
TEX0.2%——
KWR0.2%——
CGNX0.2%——
CIEN0.2%——
ESTA0.2%——
SPCX0.2%——
SCCO0.2%——
BFAM0.2%——
MOD0.2%——
TPG0.2%——
RACE0.2%——
CRCL0.2%——
AUB0.2%——
RVLV0.2%——
PSMT0.2%——
BCPC0.2%——
RYAAY0.2%——
AMX0.2%——
ESAB0.1%——
KRMN0.1%——
RSI0.1%——

Weighted by reported value in the latest 13F, held until the next filing.

PeriodReturn a yearS&P 500SharpeS&P 500Biggest dropBetaAlpha (t)
Whole backtest13 Nov 2015 to 2 Nov 2026+13.0%+14.6%0.590.76−36.1%1.13−2.4% (−1.23)
2018 onwards5 Jan 2018 to 2 Nov 2026+11.3%+13.9%0.480.66−36.1%1.12−3.1% (−1.33)
Last three years3 Nov 2023 to 2 Nov 2026+15.7%+21.8%0.691.16−21.4%1.11−6.5% (−2.02)
Last year7 Nov 2025 to 2 Nov 2026+8.1%+14.2%0.340.84−11.5%1.10−6.1% (−0.94)
DateCompanyAction
14 Aug 2026XPELBought
14 Aug 2026WBIBought
14 Aug 2026USFDBought
14 Aug 2026TSLABought
14 Aug 2026STXBought
14 Aug 2026SPCXBought
14 Aug 2026SAROBought
14 Aug 2026RMBSBought
14 Aug 2026RGENBought
14 Aug 2026PTCTBought
14 Aug 2026PRIMBought
14 Aug 2026MUBought
14 Aug 2026LRNBought
14 Aug 2026LIVNBought
14 Aug 2026LCLNBought
14 Aug 2026KRMNBought
14 Aug 2026HPEBought
14 Aug 2026HONABought
14 Aug 2026HONBought
14 Aug 2026HBMBought
14 Aug 2026HAEBought
14 Aug 2026GEVBought
14 Aug 2026GEBought
14 Aug 2026GCMGBought
14 Aug 2026FPSBought

Dated at the rebalance that made the change.

DateCompanyAction
14 Aug 2026WTWSold
14 Aug 2026WSCSold
14 Aug 2026WMSSold
14 Aug 2026WAFDSold
14 Aug 2026VRRMSold
14 Aug 2026VNETSold
14 Aug 2026VITLSold
14 Aug 2026VEEVSold
14 Aug 2026TYLSold
14 Aug 2026TXRHSold
14 Aug 2026TNETSold
14 Aug 2026TKOSold
14 Aug 2026SPOTSold
14 Aug 2026SMPLSold
14 Aug 2026SLGNSold
14 Aug 2026SHOPSold
14 Aug 2026SANMSold
14 Aug 2026RYSold
14 Aug 2026QTRXSold
14 Aug 2026PSNSold
14 Aug 2026POOLSold
14 Aug 2026PODDSold
14 Aug 2026PLNTSold
14 Aug 2026OMFSold
14 Aug 2026NTESSold

Dated at the rebalance that made the change.

Backtests are hypothetical and use today's listed companies only, which flatters results. Past performance does not predict future returns. This is research, not investment advice. How we backtest