Sandisk is joining the S&P 500 today after a huge runup in its shares. Qin Zihang / VCG via Getty Images Close Key Takeaways Shares of Sandisk climbed Friday as the data storage company joined the benchmark S&P 500 index. Sandisk's (SNDK) stock jumped close to 11% Friday morning before paring back much of its early gains. Its shares, which have been lifted by demand driven by the AI boom, are among the hottest around this year; the company was spun off from Western Digital (WDC) in February, and the stock i ...