华尔街多头认为美股上升行情仍未结束，尽管市场对人工智慧（AI）相关股票涨势过快、估值过高的担忧升温。标普500指数5月有11个交易日收于历史新高，全年迄今上涨约11%；那斯达克指数则上涨16%。第一季财报大幅优于预期，带动高盛与摩根士丹利等大型银行上调全年标普500目标，市场普遍押注AI进展、晶片与资料中心的大规模投资，将继续推升美国成长与企业获利。

AI概念股涨幅尤为惊人：费城半导体指数年初迄今飙升81%，有望写下自1999年以来最佳表现；Sandisk在2026年迄今暴涨600%，Micron、Dell Technologies、Intel、Seagate与Western Digital等相关公司亦约上涨200%。最受关注的Nvidia作为与AI热潮最密切相关、市值达5兆美元的晶片巨头，今年迄今上涨13%。这轮上涨也把估值推高，标普500目前约为未来12个月预估获利的21倍，高于过去30年平均的17倍。

尽管如此，部分投资者与量化策略师认为，强劲的企业基本面与获利成长仍可支撑行情。Morgan Stanley的Mike Wilson指出，个别股票可能出现15%至20%的回调，但整体市场仍可前进；Goldman的Ben Snider则表示，典型牛市终结讯号如投机狂热、利润率收缩或联准会升息目前都不存在。Fidelity的Denise Chisholm也认为获利成长的持久性足以合理化估值。S&P 500自2025年4月川普关税消息引发恐慌时的低点以来已反弹57%，投资人因此更倾向于逢负面消息买入而非抛售。

Wall Street bulls argue the US equity rally still has room to run despite rising fears that AI-related stocks have become overheated. The S&P 500 hit record closing highs 11 times in May and is up about 11% this year, while the Nasdaq has gained 16%. Strong first-quarter earnings have prompted major banks such as Goldman Sachs and Morgan Stanley to lift their year-end S&P targets, and investors expect AI advances plus heavy spending on chips and data centres to keep boosting growth and profits.

AI-linked shares have led the move higher. The Philadelphia Semiconductor index is up 81% year to date and is on pace for its best run since 1999; Sandisk has surged 600% in 2026 so far, while Micron, Dell Technologies, Intel, Seagate and Western Digital are each up about 200%. Nvidia, the $5tn chip giant most associated with the boom, has gained 13% this year. Valuations have climbed with the rally, leaving the S&P 500 at roughly 21 times expected earnings, above its 30-year average of 17.

Even so, many investors say strong fundamentals still support stocks. Morgan Stanley’s Mike Wilson sees pockets of excess and warns that individual shares could correct 15% to 20%, but expects the market to keep advancing; Goldman’s Ben Snider says classic end-of-bull-market signals such as speculative mania, shrinking margins or Fed hikes are absent. Fidelity’s Denise Chisholm argues durable earnings growth justifies valuations. The S&P 500 has risen 57% from its April 2025 low, reinforcing the view that buying dips has been more effective than fighting the rally.