SPY vs TMDX: Correlation
Measured on weekly returns over the past three years, SPDR S&P 500 ETF Trust (SPY) and TransMedics Group, Inc. (TMDX) carry a correlation of 0.28, a weak link.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are SPY and TMDX?
On 3 years of weekly data the SPY/TMDX correlation comes out at 0.28, weak. Recent behaviour matches the longer record: 0.33 over 1 year against 0.28 over 3. The 5-year figure is 0.32, and annualized covariance runs at 285.6 %².
Within SPY's tracked universe of 4755 assets, TMDX comes in at #2485 by 3-year correlation. Correlation aside, the last 12 months split them widely, with SPY ahead by 42.4 points (+20.6% versus -21.8%). Note the risk asymmetry: TMDX runs 4.8 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.
SPY vs TMDX: side by side
| SPY (SPDR S&P 500 ETF Trust) | TMDX (TransMedics Group, Inc.) | |
|---|---|---|
| 1-year return | +20.6% | -21.8% |
| 5-year return | +82.4% | +196.3% |
| Volatility (ann.) | 14.5% | 69.5% |
| Beta vs S&P 500 | 1.00 | 1.37 |
| Max drawdown (3Y) | -18.8% | -67.8% |
| Market cap | – | $3.2B |
| P/E (trailing) | – | 23.9 |
| Dividend yield | 1.01% | 0.00% |
| Expense ratio | 0.09% | – |
| Assets under management | $795.3B | – |
| Sector / category | ETF · US Large Cap | US Listed |
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 | SPY | TMDX |
|---|---|---|
| 2022 | -18.2% | +222.1% |
| 2023 | +26.2% | +27.9% |
| 2024 | +24.9% | -21.0% |
| 2025 | +17.7% | +95.1% |
| 2026 | +13.7% | -24.6% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are SPY and TMDX good diversifiers for each other?
Yes, to a useful degree: a correlation of 0.28 leaves real independence between the two, which historically damped combined volatility.
FAQ
What is the correlation between SPY and TMDX?
Using weekly returns as of 2026-08-27: 0.28 over 3 years, with 0.33 over the last year and 0.32 over 5 years.
Is TMDX a good diversifier for SPY?
Yes, to a useful degree: a correlation of 0.28 leaves real independence between the two, which historically damped combined volatility.
What does a correlation of 0.28 mean?
On the −1 to +1 scale, 0.28 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/spy-vs-tmdx.json
Embed this badge (it refreshes with the data), with attribution:
[](https://www.pairbook.io/pair/spy-vs-tmdx/)
No key needed, free to use. Full endpoint list in the API documentation.
Related comparisons
Hubs: SPY correlations · TMDX correlations
