WASHINGTON — Participation in the Supplemental Nutrition Assistance Program rose to 36.5 million in August 2009, up 24% from a year earlier, according to data just issued by the U.S Department of Agriculture. Kevin Concannon, U.S.D.A. undersecretary for food nutrition and consumer services, said overall SNAP participation rises during difficult economic times. The rapid expansion of SNAP (formerly the Food Stamp program) participation also was the subject of a major weekend profile by The New York Times, which said the program was growing at a rate of 20,000 people per day. The U.S.D.A. said participation in SNAP varies widely by state, ranging from a low of 47% of eligible participants to a high of 100%. "These figures underscore the importance of continuing U.S.D.A.’s efforts, in partnership with the states that operate the program directly, to ensure that potential clients are aware of the benefits of SNAP and can access those benefits easily," Mr. Concannon said.