MDY vs VTI: Correlation & Overlap
How closely do SPDR S&P MidCap 400 ETF (MDY) and Vanguard Total Stock Market ETF (VTI) trade together? Their weekly returns over three years give a correlation of 0.84, which is very strong. Looking through to holdings, 4.9% 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 VTI?
Over the past 3 years, MDY and VTI moved with a correlation of 0.84, which is very strong, meaning they move nearly in lockstep. Lately the two have drifted apart, with the 1-year correlation at 0.72 versus 0.84 over 3 years. Over 5 years the correlation is 0.89, and the annualized covariance of weekly returns is 203.3 %².
Among the 359 assets we track against MDY, VTI ranks #15 by 3-year correlation. Their 12-month results are close: +18.3% for MDY against +20.7% for VTI. The rolling one-year correlation stayed in a tight band between 0.70 and 0.93 over the past three years, which points to a structural rather than episodic relationship.
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 VTI: side by side
| MDY (SPDR S&P MidCap 400 ETF) | VTI (Vanguard Total Stock Market ETF) | |
|---|---|---|
| 1-year return | +18.3% | +20.7% |
| 5-year return | +47.5% | +74.8% |
| Volatility (ann.) | 16.5% | 14.6% |
| Beta vs S&P 500 | 0.91 | 1.01 |
| Max drawdown (3Y) | -24.0% | -19.3% |
| Dividend yield | 1.02% | 1.06% |
| Expense ratio | 0.23% | 0.03% |
| Assets under management | $26.5B | $2,290.0B |
| 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. VTI, Vanguard's Large Blend fund, carries $2,290.0B under management, 3140 holdings, a 0.03% expense ratio, a 1.06% trailing dividend yield.
Portfolio overlap between MDY and VTI
The two portfolios are largely distinct: 4.9% of the funds' weight sits in the same underlying holdings (397 common positions). Correlation tells you they move together; overlap tells you why.
| Common holding | Weight in MDY | Weight in VTI |
|---|---|---|
| TWLO | 0.95% | 0.04% |
| ILMN | 0.93% | 0.04% |
| FTI | 0.83% | 0.04% |
| CW | 0.63% | 0.04% |
| ATI | 0.80% | 0.04% |
| NVT | 0.69% | 0.03% |
| CRS | 0.66% | 0.03% |
| P | 0.94% | 0.03% |
| OKTA | 0.62% | 0.03% |
| BURL | 0.54% | 0.03% |
| XPO | 0.62% | 0.03% |
| USFD | 0.65% | 0.03% |
| UTHR | 0.60% | 0.03% |
| THC | 0.65% | 0.03% |
| WWD | 0.57% | 0.03% |
Largest positions held only by MDY: SN (0.37%), ALV (0.23%), LIVN (0.12%). Only by VTI: NVDA (6.42%), AAPL (6.31%), MSFT (4.80%), AMZN (3.66%), GOOGL (2.91%).
Overlap = sum of the smaller of the two weights across common holdings, from issuer disclosures as of 2026-08-26. Top 15 common positions shown.
Year-by-year returns
| Year | MDY | VTI |
|---|---|---|
| 2022 | -13.3% | -19.5% |
| 2023 | +16.1% | +26.0% |
| 2024 | +13.6% | +23.8% |
| 2025 | +7.2% | +17.1% |
| 2026 | +16.4% | +14.2% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are MDY and VTI good diversifiers for each other?
No. With a correlation of 0.84, MDY and VTI move nearly in lockstep, so holding both adds very little diversification.
FAQ
What is the correlation between MDY and VTI?
Using weekly returns as of 2026-08-27: 0.84 over 3 years, with 0.72 over the last year and 0.89 over 5 years.
Is VTI a good diversifier for MDY?
No. With a correlation of 0.84, MDY and VTI move nearly in lockstep, so holding both adds very little diversification.
How much do MDY and VTI overlap?
Per the issuers' own portfolio disclosures (2026-08-26), the overlap is 4.9% by weight over 397 common positions.
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Hubs: MDY correlations · VTI correlations
