Powell Industries and IES Holdings have experienced significant growth in sales to data center customers due to the increasing demand for complex computer systems driven by the growing appreciation of artificial intelligence. Powell Industries is ranked as the top-performing mid-cap company on Forbes' annual list, with its stock up 185% this year and more than 600% since the start of 2023. The list captures smaller companies in the mid-cap area of the market, which have better growth potential than large established companies and more stability and scale than small ones. Other successful mid-cap companies include Sezzle, GeneDx Holdings, Abercrombie & Fitch, Dutch Bros, Shake Shack, Sweetgreen, and Cheesecake Factory. Tariffs and other factors could benefit mid-cap companies with a domestic focus, as many companies are looking to increase production in North America rather than in Asia or other distant locations, according to Chris Welch, portfolio manager of the Diamond Hill Small-Mid Cap Fund.