SPY vs. VOO: Same S&P 500, Different 30-Year Number
SPY and VOO both track the S&P 500 — same 500 stocks, same weights, same index committee. Put $100,000 in each and hold for 30 years, and you don't get the same number back. The gap is entirely structural: a 6.45 basis-point expense ratio difference, plus a few extra basis points from how each fund handles dividends.
Assumptions: $100K lump sum, held 30 years, 10% gross annual market return before fees for both funds. SPY expense ratio 0.09%, VOO 0.03%, plus an estimated 1bp/yr cash drag on SPY. All figures nominal — sources at the end of the article.
Two Tickers, One Index
SPY (SPDR S&P 500 ETF Trust) launched in 1993 as the first US-listed ETF and still tracks the same S&P 500 index it always has. VOO (Vanguard S&P 500 ETF) launched in 2010, tracking the identical index. Both are structurally huge, both are cheap by historical fund standards, and both hold effectively the same basket of stocks in the same weights on any given day. The difference isn't what they own — it's how the fund itself is built.
| Feature | SPY | VOO |
|---|---|---|
| Sponsor | State Street | Vanguard |
| Inception | 1993 | 2010 |
| Structure | Unit Investment Trust (UIT) | Open-end fund, ETF share class |
| Expense ratio | 0.09% | 0.03% |
| Dividend handling | Held in cash, paid quarterly | Reinvested continuously |
| AUM (approx.) | ~$780B | ~$1T |
| Best suited for | Active trading, options, hedging | Buy-and-hold, long-term accumulation |
Where the Gap Actually Comes From
The headline number is the expense ratio: SPY charges 0.09% a year, VOO charges 0.03% — a 6.45 basis-point gap. That alone is small, but there's a second, less visible cost. SPY's legal structure is a Unit Investment Trust, a 1993-era design that isn't allowed to reinvest dividends internally. When the underlying companies pay dividends, SPY has to hold that cash — sometimes for a month or more between the ex-dividend date and the quarterly payout — before distributing it to shareholders. VOO's newer open-end structure reinvests dividends continuously as they arrive. In a rising market, idle cash is a drag on returns; industry estimates put this cash-drag cost at roughly 1-2 basis points a year. Add it to the expense-ratio gap and SPY runs about 8.0 basis points a year behind VOO before either fund's manager does anything active at all — because neither manager does anything active. Both funds are pure index trackers; this gap is 100% structural. It's also not just theoretical: the actual realized 10-year annualized returns of the two funds run about 7-8 basis points a year apart — in line with what the fee and cash-drag gap alone would predict.
30-Year Growth on the Same $100K
Both lines start at the same $100K and track the same underlying index. VOO compounds at 9.97%/yr net of costs; SPY compounds at 9.89%/yr net of its expense ratio and estimated cash drag.
A Gap You Can't See Until It's Big
In year one, the difference between the two lines is about $79 — invisible on any chart, irrelevant to any decision. It takes the better part of two decades for the gap to become something you'd notice without doing the math. That's the nature of a small, constant compounding disadvantage: it's not a single bad year, it's every year, quietly, for as long as you hold the fund. By year 30, the 8.0 basis points a year turns into $37K on a $100K starting position — a 2.2% larger balance for VOO, for owning the exact same 500 stocks.
Does Your Starting Balance Change the Math?
The gap is purely proportional to how much you have invested — 9.97% and 9.89% compound the same way whether you start with $10,000 or $10 million. A rollover-sized account feels the difference in real dollars a lot sooner than a starter position does.
| Starting Balance | SPY (Year 30) | VOO (Year 30) | Gap |
|---|---|---|---|
| $100K | $1.69M | $1.73M | $37K |
| $500K | $8.47M | $8.65M | $186K |
| $1.00M | $16.94M | $17.31M | $371K |
Year-by-Year Snapshot
| Year | SPY | VOO | Gap |
|---|---|---|---|
| Year 5 | $160K | $161K | $581 |
| Year 10 | $257K | $259K | $2K |
| Year 15 | $412K | $416K | $4K |
| Year 20 | $659K | $669K | $10K |
| Year 25 | $1.06M | $1.08M | $19K |
| Year 30 | $1.69M | $1.73M | $37K |
Does SPY's Liquidity Edge Matter to You?
SPY isn't losing on every dimension — it's the most heavily traded ETF on Earth, with the deepest options market by a wide margin. That matters enormously to a specific kind of investor: someone trading in and out same-day, hedging a large position with options, or running a strategy that needs to enter and exit fast at the tightest possible spread. For that user, a few extra basis points a year of expense ratio is nothing next to the cost of a wider spread on a large trade.
For a buy-and-hold retirement investor who's contributing regularly and holding for decades, that liquidity is worth close to zero — you're not trading the position often enough for spread costs to matter, and you're not using options. What you are doing is compounding a cost difference for 30 years. That's the case for VOO, or IVV, or any of the other sub-0.04%-expense S&P 500 funds: the same index, the same 500 stocks, for less.
Key Takeaways
SPY and VOO hold the same 500 stocks in the same weights — the entire 30-year gap comes from fund structure, not stock selection: a 6.45bp expense-ratio difference plus an estimated 1bp/yr cash drag from SPY's older UIT structure.
On $100K held 30 years at a 10% gross return, that's $37K — $1.73M for VOO vs. $1.69M for SPY, a gap that's invisible in year one and unmissable by year 30.
The gap scales with the market's return, not against it: at 10% the 30-year gap is $37K; at a more conservative 7% it's $17K — smaller in weaker markets, but never zero.
SPY's liquidity and options depth are real advantages for active traders and hedgers — they're not a reason for a buy-and-hold investor to pay more for the identical index.
This is a fund-structure comparison, not a market-timing or stock-picking edge. Neither fund can outperform the S&P 500 itself; the only question is how much of the index's return you actually keep.
The fund you pick barely matters if you can't stay invested through a downturn. See what missing the market's best days actually costs.
Model your own portfolio mix
Whichever S&P 500 fund you hold, the bigger question is how it fits into your full retirement plan — contributions, withdrawals, taxes, and Social Security together. Beagle runs the full 30-year projection with your actual numbers.
Sources
A note on the numbers: AUM and cash-drag figures move quarter to quarter and are approximate as of mid-2026. Expense ratios can change by prospectus amendment — check each fund's current filing before acting. This comparison assumes identical gross returns for both funds since they track the same index; it does not constitute investment advice, and past index performance does not guarantee future results. Beagle's scenario planner lets you model your actual holdings, contributions, and withdrawal strategy year by year alongside taxes and Social Security.