The stock market pushed to new highs this week, but the more notable story for analysts was the breadth of the advance. After years in which a few megacap names carried the indexes, gains are now spread across banks, industrials, and smaller companies.

Strategists at the fictional research firm Harborview Capital say the shift signals healthier footing, with investors betting on a broad economic expansion rather than a narrow technology trade. Trading volume on the floor of the New York Stock Exchange has climbed accordingly.

Cautionary voices remain. Valuations look stretched by some measures, and a broad rally can unwind as quickly as it built. But for now, the mood in Lower Manhattan is the most optimistic it has been in years.