The Russell 2000—an index of smaller US companies—returned 43.7% from April 8, 2025 through March 31, 2026, beating the S&P 500 by 11.1 percentage points over the same period, per ProShares. For an asset class that spent the better part of a decade trailing large-cap stocks, that swing matters. It has forced investors back into a structural question about small-cap health that was never cleanly settled in the first place.

The outperformance has been consistent across metrics. Fidelity Institutional confirmed small-caps beat large-caps in both the trailing 12-month period ended March 2026 and in Q1 2026 alone. The Russell Microcap index—an even tinier subset—advanced 1.5% in that first quarter and 45.8% over the prior 12 months, per Franklin Templeton, while Royce Investment Partners' USA Small Cap Index logged 27.8% over the same stretch.

The Long Underperformance in Context

This recent pop sits atop a long drag. LSEG/FTSE Russell research shows two distinct multi-year periods when small-caps lagged: 1982 to 1998, and 2010 through early 2025. The second stretch is the more telling one for today. The S&P 500 outperformed the Russell 2000 by 69% between March 2021 and early 2025, a span defined by the pandemic's outsized boost to mega-cap tech stocks and then the steepest interest-rate increases in four decades, per CME Group. Small-cap firms carry more floating-rate debt—meaning their borrowing costs rise when interest rates rise—so that repricing hit them harder.

What shifted from April 2025 forward wasn't a single new catalyst so much as the end of that tailwind. Interest rate expectations stopped climbing, the dollar weakened from its 2022–2024 peaks, and small-cap revenues, which tend to come from US domestic sales, stayed resilient in a still-growing US economy.

The Earnings Quality Problem Hasn't Gone Away

The performance gains are undeniable. So too are the underlying profit numbers, and they paint a different picture.

Aristotle Capital found that 61% of Russell 2000 companies are currently profitable—down from roughly 85% in July 1994. That 24-percentage-point drop reflects decades of index methodology that allows pre-earnings biotechs, capital-heavy startups, and cash-burning firms to join at their IPO. The Russell 2000 is a float-adjusted, yearly reconstituted benchmark, not a profitability filter. Nearly two in five constituents have zero or negative earnings.

This composition matters for interpreting the recent surge. An index-level gain of 43.7% from a low point masks a wide scatter of outcomes—profitable businesses compounding steadily, speculative bets being repriced higher, and short-covering in money-losing names that simply got swept up in the April 2025 selloff. The aggregate index return does not separate these apart.

What to Watch Going Forward

The historical comparison that keeps coming up is 1994 to 1999, when small-cap earnings quality was markedly better than it is now and the asset class still trailed large-caps for years. Today's index begins this next cycle with a structurally weaker profit base. If interest rates stay elevated, or if US growth slows, unprofitable small-caps face a real problem: they will need to borrow or refinance at yields that remain punishing relative to the pre-2022 era.

The case for small-caps looks cleaner inside screened universes where you exclude money-losing firms. Active managers who systematically filter out unprofitable companies carry very different risk than someone holding a broad index, and that gap is wider now than it was 30 years ago. The index's earnings health has degraded far more severely.

The near-term momentum is genuine. The structural caveat—that the most common way to access this rally, through the index itself, rests on a weaker earnings foundation than at any point in its modern history—is equally genuine. Both truths hold at once. For investors allocating to size factors, the difference between broad index exposure and quality-filtered small-cap exposure is not a technicality. It carries real consequences for returns.