SPY vs SPYM: 100% overlap
SPDR S&P 500 ETF Trust and State Street SPDR Portfolio S&P 500 ETF share 99.9% 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 1.0. Two funds that shared nothing would score 2.0; two identical funds score 1.0.
Top shared holdings
SPY and SPYM hold 504 of the same securities. The ten contributing most to the overlap figure:
| Holding | in SPY | in SPYM | Δ |
|---|---|---|---|
| NVDA | 7.9% | 7.9% | 0.0% |
| AAPL | 7.4% | 7.4% | 0.0% |
| MSFT | 4.4% | 4.4% | 0.0% |
| AMZN | 3.6% | 3.6% | 0.0% |
| GOOGL | 2.9% | 2.9% | 0.0% |
| AVGO | 2.9% | 2.9% | 0.0% |
| GOOG | 2.4% | 2.4% | 0.0% |
| META | 2.1% | 2.1% | 0.0% |
| MU | 1.8% | 1.8% | 0.0% |
| LLY | 1.5% | 1.5% | 0.0% |
Where SPY and SPYM 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 | SPY | SPYM | Δ |
|---|---|---|---|
| Cash & Other | 0.3% | 0.0% | +0.3pp |
| Cash and/or Derivatives | 0.0% | 0.1% | −0.1pp |
| Information Technology | 37.5% | 37.5% | +0.0pp |
| Financials | 12.4% | 12.4% | +0.0pp |
| Consumer Discretionary | 8.8% | 8.7% | +0.0pp |
| Health Care | 9.1% | 9.1% | +0.0pp |
| Communication Services | 9.3% | 9.3% | +0.0pp |
| Industrials | 8.9% | 8.9% | +0.0pp |
Δ is SPY minus SPYM, 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
0.0% of SPY by weight, held in no part of SPYM.
0.1% of SPYM by weight, held in no part of SPY.
A large count with a small weight is the usual shape: the positions one fund adds are typically its smallest ones.
Concentration and cost
| SPY | SPYM | |
|---|---|---|
| Top 10 holdings | 36.9% | 36.9% |
| Positions held | 505 | 507 |
| Cost per $10,000 held, per year | $9 | $2 |
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 SPY and SPYM overlap?
SPY and SPYM overlap 99.9% by portfolio weight — they are effectively the same fund. They share 504 holdings. The figure comes from current issuer holdings files (SPY as of 2026-07-23, SPYM as of 2026-07-23).
How is the overlap between SPY and SPYM calculated?
As the sum of the smaller weight in each fund, over every holding both funds own: Σ min(wA, wB). If SPY holds a stock at 6% and SPYM 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 SPY and SPYM?
That depends on your goals — we state facts, not advice. At 99.9% overlap, most of what one fund holds, the other holds too. Expense ratios: SPY 0.09% versus SPYM 0.02%.
What does SPY own that SPYM doesn't?
SPY holds 505 positions and SPYM holds 507; 0 of SPY's positions don't appear in SPYM at all, and they are 0.0% of SPY by weight.
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Related comparisons
Sources: issuer holdings files, SPY as of 2026-07-23, SPYM as of 2026-07-23. Weights are fractions of each fund. Diagnostics, not advice.