Big Tech's massive AI spending binge is spooking investors, who are questioning whether the billions in data center buildouts will actually pay off.

What happened

Alphabet, Amazon, Meta Platforms, and Microsoft plan to spend up to $720 billion（約120兆円） this year on AI data centers. This week, investors have grown skeptical — Amazon and Alphabet each fell about 5% on Monday, and on Tuesday chip makers Nvidia, Micron Technology, Broadcom, and Lam Research led the market lower. Alphabet is raising $80 billion（約13兆円） by selling stock and planning to spend as much as $190 billion（約30兆円） this year, while Amazon sold $54 billion（約8.6兆円） of bonds and plans to spend around $200 billion（約32兆円） on AI investments.

What to watch

Chip stocks are particularly exposed to the pullback, since they've soared on expectations of rising AI data center demand. For example, Marvell Technologies' stock has more than tripled year to date and its price-to-earnings ratio has climbed to near 100, while Sandisk shares have soared more than 700% year to date with a P/E ratio of 68 — valuations that leave little room for disappointment if AI spending slows.