FSKAX vs MDY: 5% overlap
Fidelity Total Market Index and SPDR S&P MidCap 400 ETF Trust share 4.8% 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 5 months apart — FSKAX as of 2026-02-28, 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
FSKAX and MDY hold 379 of the same securities. The ten contributing most to the overlap figure:
| Holding | in FSKAX | in MDY | Δ |
|---|---|---|---|
| CW | 0.0% | 0.8% | 0.7% |
| XPO | 0.0% | 0.7% | 0.7% |
| RGLD | 0.0% | 0.5% | 0.4% |
| WWD | 0.0% | 0.7% | 0.6% |
| ATI | 0.0% | 0.8% | 0.7% |
| UTHR | 0.0% | 0.6% | 0.6% |
| USFD | 0.0% | 0.6% | 0.6% |
| THC | 0.0% | 0.5% | 0.4% |
| ILMN | 0.0% | 0.8% | 0.8% |
| ENTG | 0.0% | 0.6% | 0.5% |
Where FSKAX 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 | FSKAX | MDY | Δ |
|---|---|---|---|
| Information Technology | 29.9% | 13.8% | +16.0pp |
| Industrials | 9.6% | 25.4% | −15.7pp |
| Communication Services | 9.7% | 1.5% | +8.2pp |
| Real Estate | 2.4% | 6.9% | −4.5pp |
| Unclassified | 4.0% | 0.0% | +4.0pp |
| Materials | 1.8% | 5.4% | −3.7pp |
| Financials | 12.2% | 14.8% | −2.6pp |
| Consumer Staples | 5.1% | 3.1% | +2.0pp |
Δ is FSKAX 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
95.7% of FSKAX by weight, held in no part of MDY.
5.8% of MDY by weight, held in no part of FSKAX.
A large count with a small weight is the usual shape: the positions one fund adds are typically its smallest ones.
Concentration and cost
| FSKAX | MDY | |
|---|---|---|
| Top 10 holdings | 32.1% | 7.6% |
| Positions held | 3,754 | 400 |
| Cost per $10,000 held, per year | $1 | $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 FSKAX and MDY overlap?
FSKAX and MDY overlap 4.8% by portfolio weight — largely distinct portfolios. They share 379 holdings. The figure comes from current issuer holdings files (FSKAX as of 2026-02-28, MDY as of 2026-07-23).
How is the overlap between FSKAX and MDY calculated?
As the sum of the smaller weight in each fund, over every holding both funds own: Σ min(wA, wB). If FSKAX 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 FSKAX and MDY?
That depends on your goals — we state facts, not advice. At 4.8% overlap, each fund still contributes meaningfully distinct exposure.
What does FSKAX own that MDY doesn't?
FSKAX holds 3,754 positions and MDY holds 400; 3,374 of FSKAX's positions don't appear in MDY at all, and they are 95.7% of FSKAX by weight.
You probably hold more than two funds
This page compares FSKAX and MDY. Paste your whole portfolio — brokerage, 401(k), IRA — and see the overlap across every fund at once, plus what you actually own underneath them and your own Effective Funds number. Free, no account, nothing stored.
X-ray my portfolio — free →Watch FSKAX vs MDY
We re-read both funds’ published holdings every weeknight. Leave an address and we'll tell you when what's inside actually changes.
Not sending yet — email alerts are built but switched off, and you'll be among the first when they turn on. No spam, one-click unsubscribe.
Related comparisons
Sources: issuer holdings files, FSKAX as of 2026-02-28, MDY as of 2026-07-23. Weights are fractions of each fund. Diagnostics, not advice.