STRO vs XBI: Correlation
Measured on weekly returns over the past three years, Sutro Biopharma, Inc. (STRO) and SPDR S&P Biotech ETF (XBI) carry a correlation of 0.54, a moderate link.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are STRO and XBI?
Across a 3-year window, the weekly returns of STRO and XBI correlate at 0.54, moderate. The link has loosened recently: the 1-year correlation (0.36) runs below the 3-year figure (0.54). Stretching to 5 years gives 0.52, with an annualized covariance of 1687.4 %².
Few assets follow STRO as closely as XBI, which ranks #1 of 13 tracked partners. Their recent paths diverged sharply: over the last 12 months STRO outperformed by 49.6 percentage points (+136.8% for STRO against +87.2% for XBI). Risk is not evenly split, since STRO carries 4.1 times the volatility of the other side.
How is this computed?
Pearson correlation on weekly returns: ρ(A,B) = cov(rA, rB) / (σA · σB), over windows of 52, 156 and 260 weeks. Covariance is annualized (×52) and expressed in %². Full definitions on the methodology page.
STRO vs XBI: side by side
| STRO (Sutro Biopharma, Inc.) | XBI (SPDR S&P Biotech ETF) | |
|---|---|---|
| 1-year return | +136.8% | +87.2% |
| 5-year return | -90.2% | +28.6% |
| Volatility (ann.) | 112.5% | 27.7% |
| Beta vs S&P 500 | 3.52 | 1.09 |
| Max drawdown (3Y) | -90.8% | -33.0% |
| Market cap | $0.4B | – |
| P/E (trailing) | – | – |
| Dividend yield | 0.00% | – |
| Sector / category | US Listed | ETF · Thematic |
Year-by-year returns
| Year | STRO | XBI |
|---|---|---|
| 2022 | -45.7% | -25.9% |
| 2023 | -46.9% | +7.6% |
| 2024 | -57.1% | +1.0% |
| 2025 | -37.1% | +35.9% |
| 2026 | +84.2% | +38.1% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are STRO and XBI good diversifiers for each other?
To a limited degree. At 0.54 the two still catch most of the same waves, so the pair smooths returns a little without insulating either from a shared selloff.
FAQ
What is the correlation between STRO and XBI?
As of 2026-08-27, the correlation of weekly returns between STRO and XBI is 0.54 over 3 years, 0.36 over 1 year and 0.52 over 5 years.
Is XBI a good diversifier for STRO?
To a limited degree. At 0.54 the two still catch most of the same waves, so the pair smooths returns a little without insulating either from a shared selloff.
What does a correlation of 0.54 mean?
On the −1 to +1 scale, 0.54 describes how much the two returns move together: +1 is lockstep, 0 is independence, negative values mean opposite directions. It says nothing about which performed better.
Use this data
$ curl https://www.pairbook.io/api/v1/pairs/stro-vs-xbi.json
Embed this badge (it refreshes with the data), with attribution:
[](https://www.pairbook.io/pair/stro-vs-xbi/)
The core API is free. Terms and every endpoint in the API documentation.
Related comparisons
Hubs: STRO correlations · XBI correlations
