AMPH vs PBYI: Correlation
How closely do Amphastar Pharmaceuticals, Inc. (AMPH) and Puma Biotechnology Inc (PBYI) trade together? Their weekly returns over three years give a correlation of 0.39, which is moderate.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are AMPH and PBYI?
On 3 years of weekly data the AMPH/PBYI correlation comes out at 0.39, moderate. Lately the two have drifted apart, with the 1-year correlation at 0.27 versus 0.39 over 3 years. The 5-year figure is 0.19, and annualized covariance runs at 1224.2 %².
Within AMPH's tracked universe of 13 assets, PBYI comes in at #7 by 3-year correlation. The last year tells two different stories: PBYI led by 109.4 percentage points, -28.2% for AMPH against +81.2% for PBYI. Note the risk asymmetry: PBYI runs 1.6 times the annualized volatility of the other leg, so equal-weighting the two is not an equal-risk position.
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.
AMPH vs PBYI: side by side
| AMPH (Amphastar Pharmaceuticals, Inc.) | PBYI (Puma Biotechnology Inc) | |
|---|---|---|
| 1-year return | -28.2% | +81.2% |
| 5-year return | +12.9% | +21.4% |
| Volatility (ann.) | 44.1% | 70.9% |
| Beta vs S&P 500 | 0.67 | 0.91 |
| Max drawdown (3Y) | -73.4% | -69.6% |
| Market cap | $0.9B | $0.5B |
| P/E (trailing) | 13.0 | 18.1 |
| Dividend yield | 0.00% | 0.00% |
| Sector / category | US Listed | US Listed |
Year-by-year returns
| Year | AMPH | PBYI |
|---|---|---|
| 2022 | +20.3% | +39.1% |
| 2023 | +120.7% | +2.4% |
| 2024 | -40.0% | -29.6% |
| 2025 | -27.9% | +95.1% |
| 2026 | -18.3% | +55.3% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are AMPH and PBYI good diversifiers for each other?
Reasonably. At 0.39, AMPH and PBYI keep a meaningful degree of independence, and combining them has historically reduced portfolio volatility.
FAQ
What is the correlation between AMPH and PBYI?
Using weekly returns as of 2026-08-27: 0.39 over 3 years, with 0.27 over the last year and 0.19 over 5 years.
Is PBYI a good diversifier for AMPH?
Reasonably. At 0.39, AMPH and PBYI keep a meaningful degree of independence, and combining them has historically reduced portfolio volatility.
What does a correlation of 0.39 mean?
On the −1 to +1 scale, 0.39 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
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Related comparisons
Hubs: AMPH correlations · PBYI correlations
