The standard S&P 500 and the S&P 500 Equal Weight Index hold essentially the same 500 companies, but they can perform very differently.
The reason is weighting. The normal S&P 500 gives larger companies more influence, while the equal-weight version resets each stock to roughly 0.2% at quarterly rebalances, according to S&P Dow Jones Indices.
Cap Weight vs Equal Weight
In the standard index, mega-cap companies such as Nvidia and Microsoft can have a much larger effect on returns.
Equal weighting reduces that concentration.
| Feature | S&P 500 | Equal Weight |
|---|---|---|
| Weighting | Market cap | Equal |
| Mega-cap influence | High | Lower |
| Rebalancing | Market driven | Quarterly |
| Typical tilt | Large growth | Smaller/value |
Because equal weight trims winners back toward 0.2%, it also creates a mild rebalancing effect.
What RSP vs SPY Tells Investors
SPY tracks the traditional S&P 500, while RSP tracks the equal-weight version.
When SPY outperforms RSP, large companies are usually driving more of the rally. When RSP strengthens relative to SPY, participation is often spreading across more stocks.
That matters during concentrated markets. Recent market breadth has at times remained narrow even as major indexes rise, with AI-linked mega-caps providing much of the upside.
The same trend is visible in the broader AI trade, where semiconductor and infrastructure stocks have attracted heavy capital flows.
Is Equal Weight Better?
Not always.
The standard S&P 500 can outperform when mega-cap leaders continue rising. Equal weight may do better when gains broaden toward smaller and value-oriented companies.
Equal weighting reduces concentration, but it can also increase exposure to weaker or smaller constituents.
For investors, the key point is simple: RSP vs SPY is also a market-breadth signal. A widening performance gap can show whether the S&P 500 rally is broad or increasingly dependent on its largest companies.