It’s being spun as a way to add an element of surprise to nominations morning. But it seems to me the motion picture academy’s surprise announcement last night that there may be as few as five Best Picture nominees next year is basically an admission the decision to expand the field to 10 beginning in 2009 was a mistake.

Under new rules adopted by the academy’s governors, Best Picture nominees will now have to score at least 5 percent of first-place votes. The press release says that PricewaterhouseCooper studied the nomination votes for 2001 to 2008 (before the slate of 10 was adopted) and determined that under the new rules, there would have been between 5 to 9 Best Picture nods in those years.

The release seems to imply that the 2010 and 2009 tallies were also studied, but the academy didn’t reveal how many Best Picture nominees there would have been in those years had the new rules been implied. I’d bet that that “Winter’s Bone” for starters wouldn’t have made the cut last year. According to the academy, the average percentage of the top vote-getter in the nominations ballot was 20.5.

“A Best Picture nomination should be an indication of extraordinary merit,” retiring Academy executive director Bruce Davis said. “If there are only eight pictures that truly earn that honor, we shouldn’t feel an obligation to round out the number.”

The decision — the actual number will not be revealed until nomination morning — will be a financial blow to Oscar consultants seeking to promote more marginal candidates for Best Picture that might slip in if the field of 10 were still mandated.

But it may reverse the devaluation of the award caused by the 10-picture field. At one point, the academy was looking at a proposal to expand the Best Director nominations to 10, since everyone knows a Best Picture nominee without a matching director nod has virtually no chance of winning.