Affordability will be one of the largest challenges in 2025 for Detroit’s automakers after General Motors Co. and Ford Motor Co. posted their best sales year in the United States since 2019, and as Stellantis NV’s declines eased somewhat in the final months of the year. Inventories swelled in 2024 following the end of pandemic-induced vehicle and microchip shortages, as well as the United Auto Workers strikes in the fall of 2023.