AI companies made up more than 40 percent of the value of U.S. equity markets before SpaceX went public in June . AI companies made up more than 40 percent of the value of U.S. equity markets before SpaceX went public in June. Indeed, of all the S&P 500’s gains in 2026, 85 percent have come from AI companies. First, AI companies are chasing what they believe will be the biggest-ever pot of gold at the end of the rainbow. Yet they are releasing models that rival the performance of those produced by the United States’ AI leaders.