DIA vs MDY: 0% overlap
SPDR Dow Jones Industrial Average ETF and SPDR S&P MidCap 400 ETF Trust share 0.0% of their portfolios by weight — computed as Σ min(wA, wB) over every holding both funds own.
You would hold two tickers and get the diversification of 2.0. Two funds that shared nothing would score 2.0; two identical funds score 1.0.
Top shared holdings
DIA and MDY hold 0 of the same securities. The ten contributing most to the overlap figure:
| Holding | in DIA | in MDY | Δ |
|---|
Where DIA and MDY differ
Sector weights as a share of each fund, ordered by the size of the gap rather than the size of the sector — two funds that overlap heavily still usually diverge somewhere.
| Sector | DIA | MDY | Δ |
|---|---|---|---|
| Financials | 28.6% | 14.8% | +13.8pp |
| Industrials | 17.5% | 25.4% | −7.9pp |
| Real Estate | 0.0% | 6.9% | −6.9pp |
| Health Care | 13.6% | 9.7% | +4.0pp |
| Communication Services | 4.7% | 1.5% | +3.2pp |
| Utilities | 0.0% | 3.1% | −3.1pp |
| Energy | 2.2% | 4.9% | −2.7pp |
| Information Technology | 15.9% | 13.8% | +2.1pp |
Δ is DIA minus MDY, in percentage points. Sector data is not published by every issuer, so “Unclassified” is a real category rather than a gap in the table.
What each fund holds alone
99.9% of DIA by weight, held in no part of MDY.
98.9% of MDY by weight, held in no part of DIA.
A large count with a small weight is the usual shape: the positions one fund adds are typically its smallest ones.
Concentration and cost
| DIA | MDY | |
|---|---|---|
| Top 10 holdings | 56.2% | 7.6% |
| Positions held | 31 | 400 |
| Cost per $10,000 held, per year | $16 | $23 |
Cost is the expense ratio applied to $10,000; it excludes any brokerage commission, bid-ask spread or tax consequence. Figures are facts about the funds, not a suggestion about which to hold.
Frequently asked
How much do DIA and MDY overlap?
DIA and MDY overlap 0.0% by portfolio weight — largely distinct portfolios. They share 0 holdings. The figure comes from current issuer holdings files (DIA as of 2026-07-23, MDY as of 2026-07-23).
How is the overlap between DIA and MDY calculated?
As the sum of the smaller weight in each fund, over every holding both funds own: Σ min(wA, wB). If DIA holds a stock at 6% and MDY holds the same stock at 4%, 4% counts as shared. The result is bounded between 0% and 100%, and it is computed after looking through any fund-of-funds to the underlying holdings.
Is it redundant to hold both DIA and MDY?
That depends on your goals — we state facts, not advice. At 0.0% overlap, each fund still contributes meaningfully distinct exposure.
What does DIA own that MDY doesn't?
DIA holds 31 positions and MDY holds 400; 30 of DIA's positions don't appear in MDY at all, and they are 99.9% of DIA by weight.
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Related comparisons
Sources: issuer holdings files, DIA as of 2026-07-23, MDY as of 2026-07-23. Weights are fractions of each fund. Diagnostics, not advice.