From the official website of the Academy Awards:
http://www.oscars.org/press/pressreleases/2009/20090624.html“After more than six decades, the Academy is returning to some of its earlier roots, when a wider field competed for the top award of the year,” said Ganis. “The final outcome, of course, will be the same – one Best Picture winner – but the race to the finish line will feature 10, not just five, great movies from 2009.”
For more than a decade during the Academy’s earlier years, the Best Picture category welcomed more than five films; for nine years there were 10 nominees. The 16th Academy Awards (1943) was the last year to include a field of that size; “Casablanca” was named Best Picture. (In 1931/32, there were eight nominees and in 1934 and 1935 there were 12 nominees.)