MDY vs SWTSX: 5% overlap
SPDR S&P MidCap 400 ETF Trust and Schwab Total Stock Market Index share 4.7% of their portfolios by weight — computed as Σ min(wA, wB) over every holding both funds own.
Different holding dates. These holdings were published about 3 months apart — SWTSX as of 2026-04-30, the rest through 2026-07-23. Each fund is compared using its most recent file, so any trading in between shows up as a difference.
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
MDY and SWTSX hold 383 of the same securities. The ten contributing most to the overlap figure:
| Holding | in MDY | in SWTSX | Δ |
|---|---|---|---|
| CW | 0.8% | 0.0% | 0.7% |
| XPO | 0.7% | 0.0% | 0.7% |
| UTHR | 0.6% | 0.0% | 0.6% |
| MTZ | 0.6% | 0.0% | 0.6% |
| P | 0.7% | 0.0% | 0.6% |
| TWLO | 0.8% | 0.0% | 0.7% |
| ENTG | 0.6% | 0.0% | 0.5% |
| WWD | 0.7% | 0.0% | 0.7% |
| CRS | 0.8% | 0.0% | 0.8% |
| ATI | 0.8% | 0.0% | 0.7% |
Where MDY and SWTSX 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 | MDY | SWTSX | Δ |
|---|---|---|---|
| Information Technology | 13.8% | 32.3% | −18.4pp |
| Industrials | 25.4% | 9.4% | +16.0pp |
| Communication Services | 1.5% | 10.1% | −8.6pp |
| Real Estate | 6.9% | 2.3% | +4.6pp |
| Materials | 5.4% | 1.6% | +3.8pp |
| Unclassified | 0.0% | 3.4% | −3.4pp |
| Financials | 14.8% | 11.9% | +3.0pp |
| Consumer Staples | 3.1% | 4.6% | −1.5pp |
Δ is MDY minus SWTSX, 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
5.0% of MDY by weight, held in no part of SWTSX.
95.1% of SWTSX by weight, held in no part of MDY.
A large count with a small weight is the usual shape: the positions one fund adds are typically its smallest ones.
Concentration and cost
| MDY | SWTSX | |
|---|---|---|
| Top 10 holdings | 7.6% | 33.9% |
| Positions held | 400 | 2,939 |
| Cost per $10,000 held, per year | $23 | $3 |
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 MDY and SWTSX overlap?
MDY and SWTSX overlap 4.7% by portfolio weight — largely distinct portfolios. They share 383 holdings. The figure comes from current issuer holdings files (MDY as of 2026-07-23, SWTSX as of 2026-04-30).
How is the overlap between MDY and SWTSX calculated?
As the sum of the smaller weight in each fund, over every holding both funds own: Σ min(wA, wB). If MDY holds a stock at 6% and SWTSX 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 MDY and SWTSX?
That depends on your goals — we state facts, not advice. At 4.7% overlap, each fund still contributes meaningfully distinct exposure.
What does MDY own that SWTSX doesn't?
MDY holds 400 positions and SWTSX holds 2,939; 16 of MDY's positions don't appear in SWTSX at all, and they are 5.0% of MDY by weight.
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Related comparisons
Sources: issuer holdings files, MDY as of 2026-07-23, SWTSX as of 2026-04-30. Weights are fractions of each fund. Diagnostics, not advice.