Deflation has varied by division, with the social sciences and natural sciences largely holding steady for the last four years. During that period, A grades have ranged from 37.1 to 37.9% in the social sciences and from 35.1 to 35.9% in the natural sciences. In the humanities and engineering, where deflation has been slower, 2008–09 brought significant movement. A's accounted for 42.5% of grades in the humanities last year and 40.6% of grades in engineering, both down two percentage points compared to 2007–08. In the period from fall 2006 through spring 2009, the most recent three-year period under the new grading policy, A's accounted for 40.1% of grades in undergraduate courses, down from 47.0% in 2001–04, the three years before the faculty adopted the policy. The 2006–09 results also mark continued deflation from those reported a year ago, when A's accounted for 40.4% of undergraduate grades in the 2005–08 period. In humanities departments, A's accounted for 44.1% of the grades in undergraduate courses in 2006–09, down from 55.6% in 2001–04. In the social sciences, there were 37.7% A grades in 2006–09, down from 43.3% in 2001–04. In the natural sciences, there were 35.6% A grades in 2006–09, compared to 37.2% in 2001–04. In engineering, the figures were 41.7% A's in 2006–09, down from 50.2% in 2001–04.