Is This ETF the Best Way to Invest in the S&P 500 in 2026?

The S&P 500 is trading at historically high valuation levels—Shiller CAPE near 40.6, a peak last seen at the dot‑com top—after a YTD gain of over 17% through Dec. 12, raising valuation concerns; the index is also highly concentrated, with Nvidia (8.46%), Apple (6.87%) and Microsoft (6.59%) alone making up nearly 22% and the top 10 holdings exceeding 40% of the index. An equal‑weight S&P 500 ETF such as Invesco’s RSP allocates roughly 0.2% to each of those mega‑caps and can serve as a hedge against concentration risk, although cap‑weighted S&P funds have materially outperformed RSP over the past decade (242% vs. 157%), while RSP has a slight edge since its 2003 inception—so investors must balance concentration and valuation risk against demonstrated recent returns when considering a switch or allocation to equal‑weight exposure.

Analysis

The S&P 500 is trading at elevated valuation levels with a Shiller price-to-earnings ratio of 40.6 and has rallied more than 17% year-to-date through Dec. 12, a valuation level the article notes has occurred only once before—at the dot-com peak—which the author flags as a reason for investor caution. This high valuation increases the risk that future returns will be muted or that a correction could be severe if earnings growth disappoints.

The index is also highly concentrated: Vanguard’s S&P 500 ETF shows Nvidia at 8.46%, Apple at 6.87%, and Microsoft at 6.59%, meaning the top three account for nearly 22% of the index and the top 10 exceed 40%. That concentration has driven the cap-weighted benchmark’s strong recent outperformance but amplifies single-stock and sector-specific downside should those mega-caps weaken.

An equal-weight alternative such as Invesco’s RSP assigns roughly 0.19%–0.25% to each of those large caps, reducing concentration while preserving broad S&P exposure. The article cites a material performance divergence—cap-weighted S&P returned 242% vs. RSP’s 157% over the past decade, though RSP slightly outperformed since its April 2003 inception—supporting RSP as a diversification hedge while noting the author’s continued preference for cap-weighted Vanguard exposure; disclosures about Motley Fool holdings may also color the commentary.

Key Decisions for Investors

• Consider adding an allocation to an equal-weight S&P ETF like RSP to hedge concentration risk in mega-cap tech while retaining a core cap-weighted S&P position
• Avoid wholesale rotation away from cap-weighted S&P funds given their decade-long outperformance; instead trim oversized mega-cap holdings selectively and rebalance proceeds into equal-weight exposure
• Monitor the Shiller CAPE (~40.6) and top‑three/index concentration (currently ~22%) as explicit re-evaluation triggers for increasing hedges, reducing equity beta, or shifting further into equal-weight exposure