Oracle's stock plunged 20% in five days after announcing $70 billion（約11兆円） in AI data center spending and $40 billion（約6.4兆円） in financing, signaling Wall Street's shift away from aggressive AI infrastructure bets.

What happened: Oracle posted Q4 2026 earnings with revenue of $19.18 billion（約3.1兆円） versus $19.1 billion（約3.1兆円） expected, but shocked investors by announcing plans to spend $70 billion（約11兆円） on AI data center buildouts in the coming year and raise $40 billion（約6.4兆円） in new debt and equity financing. The stock has fallen from expectations of reaching $1 trillion（約160兆円） and now sits just above $500 billion（約80兆円） in market cap, up only 2.3% from year-ago prices.

Why it matters: The market has decisively shifted its stance on ambitious spending plans like Oracle's. Oracle is taking on tens of billions more in debt while its long-term debt nears $100 billion（約16兆円）, contrasting sharply with Micron's strategy of cutting debt by $5.4 billion（約8600億円） through a cash tender offer in March to prepare for a potential downturn when chip prices crash if supply overtakes demand. Investors worry companies are getting overextended betting on compute demand that may not materialize as AI models become more efficient.

What to watch: The cost of frontier-level AI intelligence has dropped by some 70% to 85% over the last 18 months—users now pay a third of what they paid for GPT 4.5 early in that period. As efficiency gains continue, AI may not require hundreds of city-sized data centers, which could penalize heavy debt-financed infrastructure builders like Oracle if compute demand falls short of their bets.