FXAIX vs TSPI: 1% overlap
Fidelity 500 Index and TSP I Fund — shown via international proxy share 1.0% 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 4 months apart — FXAIX as of 2026-02-28, the rest through 2026-06-30. 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
FXAIX and TSPI hold 52 of the same securities. The ten contributing most to the overlap figure:
| Holding | in FXAIX | in TSPI | Δ |
|---|---|---|---|
| CASH | 0.3% | 2.4% | 2.1% |
| ROP | 0.1% | 0.6% | 0.6% |
| PRU | 0.1% | 0.1% | 0.0% |
| DG | 0.1% | 0.2% | 0.1% |
| DTE | 0.1% | 0.2% | 0.2% |
| ALL | 0.1% | 0.1% | 0.0% |
| MRK | 0.5% | 0.0% | 0.5% |
| TSCO | 0.0% | 0.1% | 0.0% |
| HBAN | 0.1% | 0.0% | 0.0% |
| EQT | 0.1% | 0.0% | 0.0% |
Where FXAIX and TSPI 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 | FXAIX | TSPI | Δ |
|---|---|---|---|
| Information Technology | 31.8% | 20.9% | +10.9pp |
| Financials | 12.0% | 19.7% | −7.7pp |
| Communication Services | 10.5% | 3.3% | +7.3pp |
| Unclassified | 3.3% | 9.1% | −5.8pp |
| Industrials | 8.3% | 13.8% | −5.5pp |
| Health Care | 9.6% | 5.3% | +4.3pp |
| Materials | 1.5% | 5.2% | −3.7pp |
| Consumer Discretionary | 9.7% | 7.5% | +2.2pp |
Δ is FXAIX minus TSPI, 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
95.2% of FXAIX by weight, held in no part of TSPI.
96.0% of TSPI by weight, held in no part of FXAIX.
A large count with a small weight is the usual shape: the positions one fund adds are typically its smallest ones.
Concentration and cost
| FXAIX | TSPI | |
|---|---|---|
| Top 10 holdings | 36.4% | 16.3% |
| Positions held | 506 | 8,453 |
| Cost per $10,000 held, per year | $1 | $5 |
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 FXAIX and TSPI overlap?
FXAIX and TSPI overlap 1.0% by portfolio weight — largely distinct portfolios. They share 52 holdings. The figure comes from current issuer holdings files (FXAIX as of 2026-02-28, TSPI as of 2026-06-30).
How is the overlap between FXAIX and TSPI calculated?
As the sum of the smaller weight in each fund, over every holding both funds own: Σ min(wA, wB). If FXAIX holds a stock at 6% and TSPI 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 FXAIX and TSPI?
That depends on your goals — we state facts, not advice. At 1.0% overlap, each fund still contributes meaningfully distinct exposure.
What does FXAIX own that TSPI doesn't?
FXAIX holds 506 positions and TSPI holds 8,453; 453 of FXAIX's positions don't appear in TSPI at all, and they are 95.2% of FXAIX by weight.
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Related comparisons
Sources: issuer holdings files, FXAIX as of 2026-02-28, TSPI as of 2026-06-30. Weights are fractions of each fund. Diagnostics, not advice.