XBI · WMTMT

Oct 5Oct 6Oct 7Oct 8Oct 9

30-minute bars · index reconstructed live from member prices

Breadth

89 / 157

stocks fell with the index

Concentration

100%+

of the decline from TWST, PRAX, INSM

Biggest driver

TWST −0.50

TWIST BIOSCIENCE CORP, −15.31%

Biggest offset

MRNA +0.57

MODERNA INC, +18.41%

What drove it

157 members · detractors first · 1W · residual 11.8bp within 60bp gate

The XBI fell 0.44% (−0.68 pts) on the week, but 68 of 157 members went the other way. TWST and PRAX dragged the tape lower, contributing more than the entire move.

Read the latest market-close note: Goldman and Microsoft Push the Dow to a Large Gain While Telecoms Sink Communication Services

+3.7 pts from 70 gainers−4.4 pts from 87 losers

net −0.7 pts · losers outweigh gainers 1.2 to 1

Stock

Points

Return

XBIsum of all 157 stocks

−0.7

−0.44%

TWSTTWIST BIOSCIENCE CORP

−0.5

−15.31%

PRAXPRAXIS PRECISION MEDICINES I

−0.3

−12.06%

INSMINSMED INC

−0.2

−9.47%

RVMDREVOLUTION MEDICINES INC

−0.2

−8.17%

SYRESPYRE THERAPEUTICS INC

−0.2

−8.05%

AVBPARRIVENT BIOPHARMA INC

−0.2

−40.82%

TVTXTRAVERE THERAPEUTICS INC

−0.2

−8.44%

SRRKSCHOLAR ROCK HOLDING CORP

−0.1

−9.87%

DNTHDIANTHUS THERAPEUTICS INC

−0.1

−6.62%

MDGLMADRIGAL PHARMACEUTICALS INC

−0.1

−5.54%

IMVTIMMUNOVANT INC

−0.1

−9.37%

CYTKCYTOKINETICS INC

−0.1

−4.10%

BMRNBIOMARIN PHARMACEUTICAL INC

−0.1

−4.17%

CGONCG ONCOLOGY INC

−0.1

−5.28%

CELCCELCUITY INC

−0.1

−5.77%

127 othersclick to expand the full index

−0.6

BEAMBEAM THERAPEUTICS INC

+0.1

+4.90%

AMGNAMGEN INC

+0.1

+2.94%

RXRXRECURSION PHARMACEUTICALS A

+0.1

+5.83%

IOVAIOVANCE BIOTHERAPEUTICS INC

+0.1

+2.85%

IONSIONIS PHARMACEUTICALS INC

+0.1

+4.00%

KYMRKYMERA THERAPEUTICS INC

+0.1

+4.67%

DYNDYNE THERAPEUTICS INC

+0.1

+9.47%

GILDGILEAD SCIENCES INC

+0.1

+4.44%

KODKODIAK SCIENCES INC

+0.1

+5.74%

ALNYALNYLAM PHARMACEUTICALS INC

+0.1

+5.90%

ABBVABBVIE INC

+0.1

+5.19%

NVAXNOVAVAX INC

+0.2

+21.89%

ERASERASCA INC

+0.2

+8.75%

PCVXVAXCYTE INC

+0.5

+26.38%

MRNAMODERNA INC

+0.6

+18.41%

Cap weighting, illustrated

MODERNA INC and COMPASS THERAPEUTICS INC moved almost identically (+18.41% vs +15.91%), yet MRNA moved the XBI 51.4× as much. In a cap-weighted index, the bigger company's weight turns the same percentage move into far more points.

Attribution map

slicing the −0.68 pt move · cell size = points contributed · color = direction, intensity = return

MRNA+0.6 pts(+18.4%)

TWST−0.5 pts(−15.3%)

PCVX+0.5 pts(+26.4%)

PRAX−0.3 pts

INSM−0.2 pts(−9.5%)

RVMD−0.2 pts(−8.2%)

SYRE−0.2 pts

AVBP−0.2 pts

TVTX−0.2 pts

ERAS+0.2 pts(+8.8%)

NVAX+0.2 pts(+21.9%)

SRRK−0.1 pts(−9.9%)

ABBV+0.1 pts

DNTH−0.1 pts

MDGL

ALNY+0.1 pts

KOD

IMVT

GILD+0.1 pts

DYN+0.1 pts

CYTK

KYMR

BMRN

CGON

CELC

IONS+0.1 pts

CRSP−0.1 pts

RXRX+0.1 pts

AMGN+0.1 pts

BEAM

BIIB

KRYS

MNKD

PTGX

EXEL

BBIO

MIRM

NTRA

NTLA

PRME

ORKA

ALKS

SMMT

TGTX

BHVN

IBRX

IMNM

ARWR

NKTR

RYTM

TNGX

CAPR

REGN

AVTX

IRON

ANAB

JANX

VIR

Concentration curve

cumulative share of the −0.68 pt move · sorted by contribution

When they drove it

cumulative points through the period

Breadth

member returns, this period

−50%−30%−10%+10%+30%

From −40.82% (AVBP) to +33.89% (PRME). Equal-weight, the XBI would be −0.32% vs the actual −0.44%; the gap is what cap weighting did.

By sector

point contribution · sums to −0.68 pts

-157

−0.7

The year, session by session

every trading day of 2026 · hover for the move

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SPDR S&P Biotech ETF

What drove it

Attribution map

Concentration curve

When they drove it

Breadth

By sector

The year, session by session

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