U.S. wholesalers increased their inventories in January by the largest amount in 13 months despite sharply falling sales, the government reported Friday. The Commerce Department said wholesale inventories rose 1.2 percent in January following a 0.1 percent increase the previous month. It was the biggest gain since a similar advance in December 2011. However, sales at the wholesale level dropped 0.8 percent in January after being flat the previous month. Weak growth in inventories was the key reason the economy grew only 0.1 percent in the October-December quarter. But economists believe stronger job growth and other signs of an economic rebound will spark businesses to restock this quarter. Increased stockpiling supports growth by triggering more factory production.