Has Stock Market Exuberance Become Irrational?

The S&P 500 surged 12.6% in Q2 2026, while the Nasdaq-100 jumped over 20%, yet cracks are forming beneath the rally. Margin debt hit a record $1.42 trillion, marking a 54% year-over-year increase, according to Investing.com. Semiconductor stocks have reached extremely overbought levels, signaling stretched positioning even as the AAII sentiment survey hovers near historical averages rather than euphoric extremes.

The divergence matters: traditional sentiment gauges aren't flashing red, but leverage and sector-specific positioning are at extremes. The combination suggests a mature bull phase rather than an outright bubble, though Investing.com warns investors should brace for higher volatility ahead. The record margin debt echoes conditions that preceded past consolidations, when overleveraged positions unwound rapidly once momentum stalled.

The Q2 gains pushed major indices into territory where pullbacks typically materialize, particularly when paired with record borrowing to fund stock purchases.