Invesco S&P 500 等重ETF (NYSEARCA:RSP) 已於年內上漲約 1%，而同樣追蹤標普500的市值加權ETF SPY 則下跌 3%。 this is the YTD performance gap that illustrates the advantage of equal weighting when mega‑cap concentration becomes a liability.

The rebalancing mechanism of equal‑weight indexes forces a buy‑low, sell‑high discipline that cap‑weighted indexes cannot replicate structurally. When market leadership is broad and multiple sectors participate in gains, equal‑weight funds tend to outperform; when a narrow group of mega‑caps drives almost all returns — as was the case through much of 2023 and 2024 — cap‑weighted funds hold the advantage.

The trade‑off is real: higher turnover from rebalancing, modestly higher fees in most cases, and a tendency to lag during momentum‑driven bull runs concentrated in large‑cap growth. Investors choosing equal weight are effectively betting on breadth over concentration.

Fund performance (in %):

The YTD gap is the clearest illustration of what equal weighting delivers when mega‑cap concentration becomes a liability. RSP has outperformed SPY by nearly 5 percentage points so far in 2026, a gap driven by its reduced exposure to the largest tech names that have pulled the cap‑weighted index lower.

The Invesco S&P 500 Equal Weight ETF (NYSEARCA:RSP) is the original and largest fund in this category, with nearly $91 billion in assets and an inception date of April 2003. It holds roughly 500 companies, assigning each an equal weight and rebalancing quarterly to maintain that balance.

Sector exposure diverges sharply from SPY. Instead of technology accounting for more than 30%, RSP spreads exposure across the economy: Industrials 16%, Financials 15%, Information Technology 14%. Apple, Microsoft, and Nvidia each carry roughly the same weight as a mid‑sized industrial or regional bank. This flattening is precisely what drove the +1% YTD gain while SPY was falling.

The expense ratio stands at 0.20%, higher than SPY but reasonable for the active rebalancing the strategy requires. The main caveat is the flip side of the YTD story: during the 2023 mega‑cap rebound, RSP lagged SPY by a wide margin as the “Magnificent Seven” drove most of the index’s gains. Equal weight earns its keep in broad markets, not narrow ones.

Invesco S&P 100 Equal Weight ETF (NYSEARCA:EQWL) takes a different angle. Rather than spreading across all 500 S&P constituents, it applies equal weighting only to the 100 largest U.S. companies. Every name in the portfolio is a mega‑cap or near‑mega‑cap, but no single company dominates.

This matters because the S&P 100, in its cap‑weighted form, is even more concentrated than the S&P 500. The top five or six names represent an outsized share of that index. EQWL strips out that concentration while keeping the portfolio anchored in the largest, most liquid names in the market.

The five‑year return of +67% outpaces both RSP and EUSA over that horizon, reflecting the fact that equal‑weighting within the mega‑cap tier captured upside from names like Goldman Sachs and Visa that were underweighted in cap‑weighted versions of the same index. The ‑1% YTD result is weaker than RSP’s because the fund still lives entirely within the mega‑cap world, and several of those names have sold off in 2026. Investors who want reduced concentration but are not ready to move down the market‑cap ladder will find EQWL a reasonable middle ground.

The iShares MSCI USA Equal Weighted ETF (NYSEARCA:EUSA) covers a wider universe than either RSP or EQWL. The MSCI USA index includes both large and mid‑cap U.S. equities, giving EUSA exposure to several hundred companies that never appear in the S&P 500. Each gets an equal weight.

Sector breakdown from the fund’s fact sheet shows a notably balanced portfolio: Industrials 16%, Financials 16%, Information Technology 16%, essentially three‑way parity among the top sectors. Real Estate 6% and Utilities 5%, two sectors that are structurally underweighted in cap‑heavy indexes.

The expense ratio of 0.09%, making it the cheapest option on this list, is less than half the cost of RSP’s 0.20%. Total assets stand at approximately $1.4 billion, smaller than RSP but sufficient for liquid trading. The dividend yield runs near 1.6%.

The trade‑off is the mid‑cap exposure itself. In a risk‑off environment where investors rotate toward quality and size, mid‑caps can underperform large‑caps, and EUSA will feel that more than RSP or EQWL. The five‑year return of 39% trails both peers, partly because the mid‑cap tilt has been a headwind during periods of large‑cap dominance.

Equal‑weight strategies earn their strongest returns when market leadership is broad: multiple sectors rising together, mid‑caps keeping pace with large‑caps, and no single theme or group of names driving the whole index. The 2026 YTD environment fits that description, and RSP’s outperformance reflects it.

RSP is the right starting point for most investors looking to reduce mega‑cap concentration within the S&P 500 framework. Its size, liquidity, and long track record make it the most practical choice. EQWL suits investors who want to stay within the mega‑cap universe but eliminate the lopsided weighting that makes cap‑weighted versions of the S&P 100 essentially a handful of tech bets. EUSA makes the most sense for investors who want the lowest fees and are comfortable with broader market‑cap exposure, accepting that mid‑cap volatility comes with the territory.

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分析師觀點

以我多年的市場經驗來看，等重ETF的核心價值在於它能在「廣泛布局」的環境下提供穩定超額報酬。當市場被少數mega‑cap主導時，我傾向於持有 cap‑weighted 指數，因為其能從 concentrated growth 中受益；但一旦 leadership 變得更廣，我會迅速轉向等重策略，因為它能自動以 buy‑low, sell‑high 的方式捕捉價值重新分配的機會。對於想要降低單一股票影響度，同時不想犧牲流動性的投資人，RSP 仍是最安全的起點；若想在 mega‑cap 中保持曝險卻剔除過度集中，EQWL 是很好的中間選擇；而追求最低費用、且能接受中小型股波動的投資人，則可考慮 EUSA。