Why selectivity outperforms consensus in an uncertain market
A More Demanding Environment for Growth Investing
Growth investing in 2026 demands more precision. Inflation has reaccelerated, the Fed has moved from cuts to hold, and geopolitical disruption, most acutely the escalation involving Iran, has introduced new uncertainty into energy markets and the broader macro outlook. Against that backdrop, the market has rewarded selectivity and penalized crowded consensus positions. The most crowded position in equities has been large cap growth, and mid cap growth, less index-driven and more dependent on fundamental research, offers a structurally different opportunity set.
The Structural Case: Concentration and Valuation
The data on large cap concentration is striking. The top ten positions in the S&P 500 now represent approximately 41% of the index, a level not seen in at least 25 years. Investors who own the index own, in effect, a bet on a very small number of companies. That is not diversification; it is concentration risk dressed up as passive investing.
The valuation gap compounds the concern. The S&P 500 trades at 28.0x trailing twelve-month earnings; the S&P MidCap 400 trades at 22.1x, a 21.1% discount. The same secular growth themes driving large cap valuations are expressed across the mid cap universe at materially more attractive entry points.
Source: FactSet, as of May 11, 2026 | Trailing 12m P/E, Weighted Harmonic Average | S&P 500 vs. S&P MidCap 400
This combination of historical crowding at the index level and a persistent valuation discount in mid cap creates conditions that have historically favored active management. When mean reversion occurs, it tends to be sharp. Managers building positions in mid cap growth companies with strong earnings trajectories are positioned ahead of that rotation, not reacting to it.
Where the Opportunity Is: Specific Themes, Not Sector Bets
The mid cap opportunity is not a sector call; it is a collection of company-specific ideas tied to durable secular themes. Energy infrastructure is one of the more compelling: LNG export businesses with approximately 90% contracted revenue offer stable cash flow with upside optionality on spot pricing, valued at roughly 16x earnings. The electrification of the US economy and the buildout of AI infrastructure represent a second cluster of electrical infrastructure contractors, copper producers, and grid modernization specialists with visible earnings tied to multi-year hyperscaler and utility capex cycles. Mid cap captures this exposure earlier and with more precision than large cap indices.
Healthcare and financials round out the opportunity set. Commercial-stage biopharma with near-term catalysts including rare disease platforms, novel drug mechanisms, and M&A target profiles are not names that traditionally surface through passive screening. Rather, they can reward a dedicated fundamental research approach. In financials, P&C underwriters at single-digit multiples, B2B payments compounders, and alternative asset managers represent businesses with durable competitive positions that do not appear in passive benchmarks but reward active coverage.
Discipline as a Return Driver
A high-conviction mid cap approach is only as good as its discipline. The wider opportunity set exists precisely because mid cap is less efficiently priced, but inefficiency cuts both ways. Position sizing is conviction-driven, not benchmark-driven. Rotation happens when the fundamental thesis has been impaired, not when a stock is down or the macro narrative shifts. Adds on weakness are reserved for cases of high conviction with the original investment case intact.
The result is a portfolio that looks meaningfully different from the benchmark, with active weights that are deliberate, concentration managed explicitly across themes, and every position required to earn its place. That is not risk aversion. It is process.
Selectivity as the Sustainable Edge
Markets that reward consensus positioning eventually stop doing so. The rotation away from mega-cap concentration building through 2025 and into 2026 reflects exactly that dynamic. Mid cap growth, with its wider opportunity set, more attractive valuations, and less efficiently priced securities, is where skilled fundamental research continues to generate real alpha. In a market that demands precision, that is not a style preference. It is a structural advantage.
This material is for informational purposes only and should not be construed as investment advice or a recommendation to buy or sell any security. Past performance is not indicative of future results. All investments involve risk, including loss of principal. Westfield Capital Management Company, L.P. is a registered investment adviser.
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