NBBK vs SPY: Correlation
How closely do NB Bancorp, Inc. (NBBK) and SPDR S&P 500 ETF Trust (SPY) trade together? Their weekly returns over three years give a correlation of 0.44, which is moderate.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are NBBK and SPY?
Across a 3-year window, the weekly returns of NBBK and SPY correlate at 0.44, moderate. The past 12 months show a weaker link (0.15) than the 3-year average (0.44). Stretching to 5 years gives n/a, with an annualized covariance of 176.0 %².
Within NBBK's tracked universe of 17 assets, SPY comes in at #8 by 3-year correlation. Twelve-month performance is nearly a tie, at +19.3% for NBBK and +20.6% for SPY. One caveat on sizing: NBBK is 1.9 times as volatile as the other leg, so an equal-dollar split is far from equal-risk.
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.
NBBK vs SPY: side by side
| NBBK (NB Bancorp, Inc.) | SPY (SPDR S&P 500 ETF Trust) | |
|---|---|---|
| 1-year return | +19.3% | +20.6% |
| 5-year return | n/a | +82.4% |
| Volatility (ann.) | 27.6% | 14.5% |
| Beta vs S&P 500 | 0.84 | 1.00 |
| Max drawdown (3Y) | -24.7% | -18.8% |
| Market cap | $1.0B | – |
| P/E (trailing) | 14.7 | – |
| Dividend yield | 4.39% | 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 | NBBK | SPY |
|---|---|---|
| 2022 | – | -18.2% |
| 2023 | – | +26.2% |
| 2024 | +34.3% | +24.9% |
| 2025 | +10.6% | +17.7% |
| 2026 | +13.9% | +13.7% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are NBBK and SPY good diversifiers for each other?
Reasonably. At 0.44, NBBK and SPY keep a meaningful degree of independence, and combining them has historically reduced portfolio volatility.
FAQ
What is the correlation between NBBK and SPY?
The NBBK/SPY correlation stands at 0.44 on a 3-year window (1 year: 0.15, 5 years: n/a), computed from weekly returns as of 2026-08-27.
Is SPY a good diversifier for NBBK?
Reasonably. At 0.44, NBBK and SPY keep a meaningful degree of independence, and combining them has historically reduced portfolio volatility.
What does a correlation of 0.44 mean?
Correlation ranges from −1 to +1. Values near +1 mean two assets move together, near 0 that they move independently, and negative values that they tend to move in opposite directions. It measures co-movement, not performance.
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Related comparisons
Hubs: NBBK correlations · SPY correlations
