Economist Paul Krugman said massive AI data-center spending is crowding out investment in housing, offices and factories by increasing private credit demand and lifting interest rates. Ray Dalio called the expansion a classic bubble nearing a breaking point, while Galaxy Digital CEO Michael Novogratz described it as the biggest speculative bubble of his lifetime but urged investors to buy AI stocks because typical collapse signals have not appeared. Jamie Dimon estimates hyperscaler ecosystem spending at roughly $700 billion in 2026 and nearly $1 trillion in 2027, while global AI-linked debt issuance could approach $570 billion and UBS estimates 2026 capital expenditure may consume nearly 100% of hyperscalers' operating cash flow. Nvidia's market capitalization approached $6 trillion as AI shares helped push the S&P 500 and Nasdaq 100 to records, increasing concerns about valuation and market concentration.