U.S. workers spent 4.9 billion minutes using an instant messaging service during the past year, according to a Jupiter Media Matrix report, as unique users increased 34 percent to 13.4 million (or an average of about 6 hours per user). Instant messaging at home, meanwhile, rose 48 percent to 13.6 billion total minutes. America Online, with its AIM and ICQ services, continues to hold the top spot, with 41.7 home users. MSN increased its market share by 94 percent to 18.5 million users, while Yahoo! captured the third spot with 11.9 million users. Among work users, America Online has 8.8 million users, MSN has about 4.8 million, and Yahoo has 3.4 million.