S&P 1
vs S&P 500
Imagine a one-stock index: each month you buy whichever company is the biggest in America. AT&T, then IBM, then Exxon, GE, Microsoft, Apple, Nvidia… How does the throne compare with the whole kingdom? We backtested it with real crown-holders and real returns — and the answer surprised us.
The one-stock index — tested with real data
Call it the S&P 1: a strategy that holds exactly one stock — whichever company is the largest in the American market — and switches whenever the crown changes hands. Academic studies long suggested the crown lags the market. So we tested it properly: real crown-holders each year (largest US company by first-quarter market cap, per American Business History Center records) and real annual total returns with dividends, sourced from SEC proxy statements and published return tables, 1995–2025.
From 2000 (dot-com peak): crown $61,412 vs index $73,885 — index wins
From 2005: crown $242,121 vs index $83,070 — crown wins 2.9×
From 2012: crown $126,190 vs index $69,367 — crown wins 1.8×
Over the full 31 years the crown compounded at 13.1% a year against the index's 11.0%. The strategy's one kill-zone is entering at a mania peak: a 2000 start buys Microsoft at its dot-com top (−63% that year) and never fully recovers the gap. From nearly every other start, the throne beat the kingdom — the annual switching even routed around Microsoft's lost decade by holding ExxonMobil from 2005 to 2011.
Who has worn the crown
The throne has changed dynasties roughly once a technological era:
Notice what the list is really telling you: every previous king was eventually dethroned. AT&T was broken up. IBM missed the PC's implications. GE fell from grace entirely. The company that looks unbeatable at #1 is, historically, closer to its peak than its beginning.
What the research found
This isn't just a story — it's a measured effect. Research by Dimensional Fund Advisors found that companies dramatically outperform the market on their way into the top ten, then lag it in the years after arriving — on the order of one to two percentage points a year over the following decade. Research Affiliates reached a similar verdict in a study bluntly titled "Too Big to Succeed": the top dog in each sector tended to underperform its peers in the decade after taking the crown. Size attracts competition, regulation, and the simple arithmetic that doubling a giant is far harder than doubling an upstart.
The S&P 1 side applies those same years minus a "top-dog drag" —
defaulted to 1.5%/yr per the research above, adjustable 0–5%.
A precise month-by-month #1-stock return series doesn't exist
as clean public data, so we model the documented effect
rather than invent false precision.
Why a small drag becomes a huge gap
One and a half percent a year sounds survivable. Compounded over 35 years, it isn't small at all — the shortfall typically compounds to a third or more of the final pot. That's the quiet lesson of the whole page: in compounding, persistent small edges beat dramatic bets, and the index's edge over the throne is persistent.
The case for the kingdom
The S&P 500 never has to guess who wins the next era. When IBM faded, the index already owned Microsoft. When GE crumbled, it already owned Apple. When the AI era arrived, it already owned Nvidia. Buying the whole kingdom means automatically holding every future king before anyone knows their name — which is precisely what a one-stock strategy can never do. To see what the kingdom itself compounded to, run the S&P 500 since-inception calculator with real returns from any start year.
Two truths, honestly held
The century-long academic studies (Dimensional, Research Affiliates) still stand: measured from the 1920s onward, companies on average lag the market after reaching the very top — AT&T, IBM and GE all eventually proved it. But the 1995–2025 window is the concentration era, and in it the implementable strategy won. Both facts belong on this page. Nobody knows which regime the next thirty years brings — that uncertainty is the honest takeaway.
Switching is annual, on Q1 market caps — Nvidia's mid-year crown moments never register
One stock = one company's blow-up risk; the index diversifies it away
S&P 1 vs S&P 500 FAQ
As of 2024–2026 the crown has traded between Nvidia, Microsoft and Apple, with Nvidia becoming the first company to reach a $4 trillion market value in 2025. The largest company changes with market prices, sometimes daily.
In the real 1995–2025 backtest on this page, mostly yes: $10,000 in the crown strategy from 1995 grew to about $449,000 versus $257,000 in the index (13.1% vs 11.0% a year). The big exception is starting at the 2000 dot-com peak, where the index wins. Century-long studies still find the crown lags on average — this window was the concentration era.
By the time a company is the largest, its fastest growth is usually behind it. Sheer size makes further doubling arithmetically harder, and dominance attracts competition and regulatory attention. Most past #1s — AT&T, IBM, GE — were eventually dethroned.
In rough sequence: AT&T (trading with General Motors) through the mid-20th century, IBM from the late 1960s through the 1980s, Exxon around 1990, GE and Microsoft through the 1990s and 2000s, ExxonMobil from 2006 to 2011, Apple for most of 2011 to 2023, and Nvidia, Microsoft and Apple trading the title since 2024.
Yes — in real-data mode. The crown each year is the largest US company by Q1 market cap (American Business History Center records), and its annual total returns with dividends come from SEC proxy statements and published return tables, 1995–2025. The S&P 500 side uses real published annual total returns. Model mode additionally lets you apply any drag or edge to explore other assumptions.