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US mid caps: A comeback for the quiet outperformer?

US mid-cap stocks have outperformed US large caps by 322% cumulatively since the start of the 2000s.  The raise of mega-cap tech, combined with broader uncertainty, have hindered outperformance of late, but with macro and policy dynamics improving, leadership can broaden toward mid-caps—supported by attractive valuations and an expected earnings growth rebound. 

Temps de lecture: 5 min
Senior Equity ETF Strategist

The S&P MidCap 400 Index has delivered strong long‑term outperformance relative to the S&P 500 as far back as 1999, although it has lagged in the past three years amid uncertainty and mega‑cap tech dominance. Looking ahead, an improving macro and policy backdrop—coupled with a reaccelerating US economy—creates room for market leadership to broaden. Mid caps are well placed to benefit, supported by attractive valuations and an expected earnings growth rebound. They offer higher quality than small caps but maintain a domestic revenue tilt. US mid caps serve as a compelling tool to seek enhanced returns and strengthen portfolio diversification.

The best of both worlds

US mid‑cap equities sit in a sweet spot between large and small caps. They give investors access to economic exceptionalism and trade at relatively undemanding valuation multiples. They retain the high‑growth potential of small caps but include more established businesses with easier access to capital.1

The best‑known mid‑cap exposure is the S&P MidCap 400 Index, which consists of companies with a median market capitalisation of USD $7.3 billion.2 S&P MidCap 400’s total market capitalisation is USD $3.4 trillion—larger than major large‑cap European indices such as MSCI France, MSCI UK, and MSCI Germany.3 It is not a niche exposure—but it is often overlooked by investors outside the US. 

 

Domestic and cyclical exposure

The S&P MidCap 400 Index offers a more direct exposure to a reaccelerating US economy than large caps, generating approximately 75% of its revenue within the US, versus 58% for the S&P 500.4 The S&P MidCap 400 is also less concentrated: the top 10 companies represent only 7% of index weight, compared with 39% for the S&P 500.5 Sector distribution is more balanced, with 24% in Industrials, 17% in Financials, and 14% in Information Technology (vs. 34% for the S&P 500). Mid caps also are more cyclical and better positioned to benefit from improving macro and policy dynamics.

Macro and policy dynamics turn positive

Although the US economy continues to beat expectations, macroeconomic and policy uncertainties have slowed mid‑cap equity performance. Recession concerns and inflation, followed by trade‑related disruptions, caused mid caps to offer only sporadic periods of outperformance versus the S&P 500.

Macro and policy factors are now more favourable:

  • The One Big Beautiful Bill Act provides tax incentives for consumers and companies.
  • Ongoing deregulation supports Financials and other sectors.
  • Midterm election season may prompt additional incentives from the Trump administration and limit the risk of restrictive policy steps.

Bottom line: State Street Investment Management economists anticipate the US economy will reaccelerate to 2.3%,6 comfortably outpacing most developed economies. The Federal Reserve is likely to continue easing.

In our view, the combination of economic reacceleration and limited systemic risks creates a Goldilocks environment that supports a sustained broadening of market performance into cyclical mid‑cap equities.

A timely entry point?

Since the beginning of the 2000s, the S&P MidCap 400 Index has cumulatively outperformed the S&P 500 by 322%. The 12‑month rolling relative return averaged 1.8%, making US mid caps useful for long‑term investors seeking to enhance returns and diversify portfolios. As growth reaccelerates, policies become supportive, and uncertainty fades, we believe the recent dip in 12‑month relative performance—now below its historical one‑standard‑deviation range—may have reached a bottom and could signal an attractive entry point.

US exceptionalism at a reasonable price

The S&P MidCap 400 Index trades at a 1‑year forward P/E of 16.2x, below its 10‑year average, an attractive level given the supportive US macro and policy environment. Mid caps trade at a 26% 1‑year forward P/E discount to the S&P 500, putting the discount in the top 5% of the past 10 years. The broad market-cap-weighted S&P MidCap 400 Index offers a compelling way to access US growth at a more reasonable price, especially while US valuation levels remain a key concern for investors. 

A sustained rally built on earnings-per-share growth?

Tailwinds of lower rates, firmer economic growth, and deregulation are expected to support US mid-cap earnings more than large caps in 2026. In our view, earnings-per-share (EPS) expansion remains the most important precondition for the S&P MidCap 400 Index to return to robust, long‑term performance.

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