The S&P 500 closed above 6,000 for the first time on Monday, after the index touched 5,000 on 9 February, and since then, energy company Vistra and data analytics firm Palantir have driven the rally with gains of 237% and 147%, respectively.Vistra and Palantir, which were added to the S&P 500 in May and September, respectively, have both been companies were both boosted by the artificial intelligence boom.