American colleges and universities raised an estimated $28-billion in private donations in the 2006 fiscal year — $2.4-billion, or 9.4-percent, more than in 2005, according to a report released on Wednesday by the Council for Aid to Education. The significant jump, the biggest one-year increase since 2000, was the result of larger donations from alumni and other individual donors, many of whom were solicited through numerous major fund-raising campaigns.