MDY vs VOO: Correlation & Overlap
SPDR S&P MidCap 400 ETF (MDY) and Vanguard S&P 500 ETF (VOO) show a very strong relationship: their 3-year correlation of weekly returns is 0.80. Looking through to holdings, 0% of the two portfolios is the same by weight.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are MDY and VOO?
On 3 years of weekly data the MDY/VOO correlation comes out at 0.80, very strong, meaning they move nearly in lockstep. Lately the two have drifted apart, with the 1-year correlation at 0.66 versus 0.80 over 3 years. The 5-year figure is 0.86, and annualized covariance runs at 190.2 %².
Within MDY's tracked universe of 359 assets, VOO comes in at #21 by 3-year correlation. Neither side won the trailing year by much: +18.3% against +20.6%. On a rolling one-year basis the correlation drifted between 0.64 and 0.91, a moderate band.
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.
MDY vs VOO: side by side
| MDY (SPDR S&P MidCap 400 ETF) | VOO (Vanguard S&P 500 ETF) | |
|---|---|---|
| 1-year return | +18.3% | +20.6% |
| 5-year return | +47.5% | +83.0% |
| Volatility (ann.) | 16.5% | 14.4% |
| Beta vs S&P 500 | 0.91 | 0.99 |
| Max drawdown (3Y) | -24.0% | -18.7% |
| Dividend yield | 1.02% | 1.07% |
| Expense ratio | 0.23% | 0.03% |
| Assets under management | $26.5B | $1,686.9B |
| Sector / category | ETF · US Small & Mid Cap | ETF · US Large Cap |
MDY, State Street Investment Management's Mid-Cap Blend fund, carries $26.5B under management, 400 holdings, a 0.23% expense ratio, a 1.02% trailing dividend yield. VOO, Vanguard's Large Blend fund, carries $1,686.9B under management, 503 holdings, a 0.03% expense ratio, a 1.07% trailing dividend yield.
Portfolio overlap between MDY and VOO
The two portfolios are largely distinct: 0% of the funds' weight sits in the same underlying holdings (0 common positions). Correlation tells you they move together; overlap tells you why.
Largest positions held only by MDY: TWLO (0.95%), P (0.94%), ILMN (0.93%), FTI (0.83%), ATI (0.80%). Only by VOO: NVDA (7.56%), AAPL (7.05%), MSFT (5.37%), AMZN (4.13%), GOOGL (3.25%).
Overlap = sum of the smaller of the two weights across common holdings, from issuer disclosures as of 2026-08-26.
Year-by-year returns
| Year | MDY | VOO |
|---|---|---|
| 2022 | -13.3% | -18.2% |
| 2023 | +16.1% | +26.3% |
| 2024 | +13.6% | +25.0% |
| 2025 | +7.2% | +17.8% |
| 2026 | +16.4% | +13.7% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are MDY and VOO good diversifiers for each other?
No. With a correlation of 0.80, MDY and VOO move nearly in lockstep, so holding both adds very little diversification.
FAQ
What is the correlation between MDY and VOO?
As of 2026-08-27, the correlation of weekly returns between MDY and VOO is 0.80 over 3 years, 0.66 over 1 year and 0.86 over 5 years.
Is VOO a good diversifier for MDY?
No. With a correlation of 0.80, MDY and VOO move nearly in lockstep, so holding both adds very little diversification.
How much do MDY and VOO overlap?
0% by weight, across 0 common holdings, based on issuer-disclosed portfolios as of 2026-08-26.
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Hubs: MDY correlations · VOO correlations
