MDY vs XLK: Correlation & Overlap
Measured on weekly returns over the past three years, SPDR S&P MidCap 400 ETF (MDY) and Technology Select Sector SPDR Fund (XLK) carry a correlation of 0.63, a strong link. The two funds also share 0% of their portfolios by weight.
Data as of 2026-08-27 · refreshed every trading day · weekly returns · methodology
How correlated are MDY and XLK?
On 3 years of weekly data the MDY/XLK correlation comes out at 0.63, strong. Lately the two have drifted apart, with the 1-year correlation at 0.50 versus 0.63 over 3 years. The 5-year figure is 0.70, and annualized covariance runs at 247.8 %².
By 3-year correlation, XLK places #143 of the 359 assets tracked against MDY. The last year tells two different stories: XLK led by 25.1 percentage points, +18.3% for MDY against +43.4% for XLK. The rolling one-year correlation moved between 0.43 and 0.81 over the past three years, a moderate range.
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 XLK: side by side
| MDY (SPDR S&P MidCap 400 ETF) | XLK (Technology Select Sector SPDR Fund) | |
|---|---|---|
| 1-year return | +18.3% | +43.4% |
| 5-year return | +47.5% | +145.2% |
| Volatility (ann.) | 16.5% | 24.0% |
| Beta vs S&P 500 | 0.91 | 1.50 |
| Max drawdown (3Y) | -24.0% | -25.7% |
| Dividend yield | 1.02% | 0.45% |
| Expense ratio | 0.23% | 0.08% |
| Assets under management | $26.5B | $115.4B |
| Sector / category | ETF · US Small & Mid Cap | Sector ETF |
On the fund side, MDY sits in the Mid-Cap Blend category at State Street Investment Management, with $26.5B under management, 400 holdings, a 0.23% expense ratio, a 1.02% trailing dividend yield. On the fund side, XLK sits in the Technology category at State Street Investment Management, with $115.4B under management, 73 holdings, a 0.08% expense ratio, a 0.45% trailing dividend yield.
Portfolio overlap between MDY and XLK
The two portfolios are largely distinct. Weighing the shared positions, 0% of the two funds is identical, spread across 0 common holdings. That shared book is a large part of why the returns line up.
Largest positions held only by MDY: TWLO (0.95%), P (0.94%), ILMN (0.93%), FTI (0.83%), ATI (0.80%). Only by XLK: NVDA (13.91%), AAPL (12.61%), MSFT (10.10%), AVGO (4.61%), AMD (4.09%).
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 | XLK |
|---|---|---|
| 2022 | -13.3% | -27.7% |
| 2023 | +16.1% | +56.0% |
| 2024 | +13.6% | +21.6% |
| 2025 | +7.2% | +24.6% |
| 2026 | +16.4% | +31.3% |
Calendar-year price returns; the current year is year-to-date as of the data date above.
Are MDY and XLK good diversifiers for each other?
To a limited degree. At 0.63 the two still catch most of the same waves, so the pair smooths returns a little without insulating either from a shared selloff.
FAQ
What is the correlation between MDY and XLK?
As of 2026-08-27, the correlation of weekly returns between MDY and XLK is 0.63 over 3 years, 0.50 over 1 year and 0.70 over 5 years.
Is XLK a good diversifier for MDY?
To a limited degree. At 0.63 the two still catch most of the same waves, so the pair smooths returns a little without insulating either from a shared selloff.
How much do MDY and XLK overlap?
The two funds share 0 holdings amounting to 0% of weight, per issuer portfolio files dated 2026-08-26.
Use this data
$ curl https://www.pairbook.io/api/v1/pairs/mdy-vs-xlk.json
Markdown for the live badge, attribution link included:
[](https://www.pairbook.io/pair/mdy-vs-xlk/)
The core API is free. Terms and every endpoint in the API documentation.
Related comparisons
Hubs: MDY correlations · XLK correlations
