MGK vs SPY: 50% overlap
Vanguard Mega Cap Growth ETF and SPDR S&P 500 ETF Trust share 50.1% 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 1.5. Two funds that shared nothing would score 2.0; two identical funds score 1.0.
Top shared holdings
MGK and SPY hold 54 of the same securities. The ten contributing most to the overlap figure:
| Holding | in MGK | in SPY | Δ |
|---|---|---|---|
| NVDA | 13.2% | 7.9% | 5.3% |
| AAPL | 12.1% | 7.4% | 4.7% |
| MSFT | 7.5% | 4.4% | 3.0% |
| AMZN | 4.4% | 3.6% | 0.9% |
| GOOGL | 5.9% | 2.9% | 3.0% |
| AVGO | 4.3% | 2.9% | 1.3% |
| GOOG | 4.6% | 2.4% | 2.3% |
| META | 4.1% | 2.1% | 2.0% |
| LLY | 3.4% | 1.5% | 1.9% |
| TSLA | 3.9% | 1.4% | 2.5% |
Where MGK and SPY 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 | MGK | SPY | Δ |
|---|---|---|---|
| Information Technology | 58.6% | 37.5% | +21.1pp |
| Financials | 4.0% | 12.4% | −8.4pp |
| Communication Services | 16.2% | 9.3% | +6.9pp |
| Industrials | 2.6% | 8.9% | −6.3pp |
| Health Care | 4.9% | 9.1% | −4.2pp |
| Consumer Staples | 0.4% | 4.6% | −4.2pp |
| Energy | 0.0% | 3.4% | −3.4pp |
| Consumer Discretionary | 11.2% | 8.8% | +2.4pp |
Δ is MGK minus SPY, 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
1.3% of MGK by weight, held in no part of SPY.
49.8% of SPY by weight, held in no part of MGK.
A large count with a small weight is the usual shape: the positions one fund adds are typically its smallest ones.
Concentration and cost
| MGK | SPY | |
|---|---|---|
| Top 10 holdings | 63.5% | 36.9% |
| Positions held | 57 | 505 |
| Cost per $10,000 held, per year | $5 | $9 |
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 MGK and SPY overlap?
MGK and SPY overlap 50.1% by portfolio weight — substantial duplication if you hold both. They share 54 holdings. The figure comes from current issuer holdings files (MGK as of 2026-06-30, SPY as of 2026-07-23).
How is the overlap between MGK and SPY calculated?
As the sum of the smaller weight in each fund, over every holding both funds own: Σ min(wA, wB). If MGK holds a stock at 6% and SPY 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 MGK and SPY?
That depends on your goals — we state facts, not advice. At 50.1% overlap, each fund still contributes meaningfully distinct exposure.
What does MGK own that SPY doesn't?
MGK holds 57 positions and SPY holds 505; 3 of MGK's positions don't appear in SPY at all, and they are 1.3% of MGK by weight.
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Related comparisons
Sources: issuer holdings files, MGK as of 2026-06-30, SPY as of 2026-07-23. Weights are fractions of each fund. Diagnostics, not advice.