Sales for U.S. retailers have increased by about 4% so far this holiday season as Americans balanced tighter budgets with a desire to upgrade gadgets and refresh wardrobes, according to preliminary figures released by Visa and Mastercard on Tuesday. Shoppers were more deliberate with their purchases, often using artificial intelligence tools to discover and compare prices so that they could stretch discretionary budgets, Visa's chief economist, Wayne Best, said in a statement. Michelle Meyer, chief economist at Mastercard Economics Institute, added that consumers shopped early and leaned on promotions to get the best deals.