BST vs SPY: Correlation
Measured on weekly returns over the past three years, BlackRock Science and Technology Trust (BST) and SPDR S&P 500 ETF Trust (SPY) carry a correlation of 0.83, a very strong link.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are BST and SPY?
Over the past 3 years, BST and SPY moved with a correlation of 0.83, which is very strong, meaning they move nearly in lockstep. Little has changed lately, as the 1-year reading of 0.78 lands near the 3-year figure. Over 5 years the correlation is 0.86, and the annualized covariance of weekly returns is 266.1 %².
Among the 25 assets we track against BST, SPY ranks #7 by 3-year correlation. Their recent paths diverged sharply: over the last 12 months BST outperformed by 20.1 percentage points (+40.7% for BST against +20.6% for SPY). Note the risk asymmetry: BST runs 1.5 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.
BST vs SPY: side by side
| BST (BlackRock Science and Technology Trust) | SPY (SPDR S&P 500 ETF Trust) | |
|---|---|---|
| 1-year return | +40.7% | +20.6% |
| 5-year return | +46.7% | +82.4% |
| Volatility (ann.) | 22.2% | 14.5% |
| Beta vs S&P 500 | 1.27 | 1.00 |
| Max drawdown (3Y) | -23.4% | -18.8% |
| Market cap | – | – |
| P/E (trailing) | 6.9 | – |
| Dividend yield | 0.00% | 1.01% |
| Expense ratio | – | 0.09% |
| Assets under management | – | $795.3B |
| Sector / category | US Listed | ETF · US Large Cap |
SPY is a Large Blend fund from State Street Investment Management: $795.3B under management, 504 holdings, a 0.09% expense ratio, a 1.01% trailing dividend yield.
Year-by-year returns
| Year | BST | SPY |
|---|---|---|
| 2022 | -38.3% | -18.2% |
| 2023 | +30.1% | +26.2% |
| 2024 | +18.0% | +24.9% |
| 2025 | +23.7% | +17.7% |
| 2026 | +30.9% | +13.7% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are BST and SPY good diversifiers for each other?
No: a correlation of 0.83 means BST and SPY tend to fall together, which is precisely when diversification is supposed to help.
FAQ
What is the correlation between BST and SPY?
The BST/SPY correlation stands at 0.83 on a 3-year window (1 year: 0.78, 5 years: 0.86), computed from weekly returns as of 2026-08-27.
Is SPY a good diversifier for BST?
No: a correlation of 0.83 means BST and SPY tend to fall together, which is precisely when diversification is supposed to help.
What does a correlation of 0.83 mean?
On the −1 to +1 scale, 0.83 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.
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Hubs: BST correlations · SPY correlations
