Thomas Fuller / SOPA Images / LightRocket / Getty Images Sandisk shares have gained roughly 500% this year, far more than the biggest gainers in the S&P 500. Inclusion in an index, especially a major one like the S&P 500, often provides a boost to stocks as it can introduce the company to a new audience of investors. Sandisk stock has been a huge gainer this year, climbing as its business has benefited from demand for memory driven by the AI buildout; its stock, up more than 500% in 2025, has substantially ...