Efficient Market?

After hours on October 13, 2010, Apollo announced changes in its admission policy in an investor conference call, and stated that the policy changes would likely reduce the number of new admissions. The policy requires new students to pass a three week trial class, before being admitted to the university. The specific language that seems to have caused such a reaction is:

Given the uncertainties, we are withdrawing the business outlook for fiscal year 2011 which we previously provided. For the first quarter the impact of the changes we are making as well as the various external factors could result in a decline in new degreed enrollments in excess of 40% year-over-year. http://www.apollogrp.edu/Investor/Transcripts/APOL-Transcript-Q410.pdf

At first glance, the reaction of the market seems to illustrate the very efficient way in which new information is rapidly reflected in price. On the other hand, the new policy came after a year-long pilot program at some campuses, a summer of congressional hearings, and a prior announcement to thousands of staff and faculty members concerning plans to implement this new policy.

One possible explanation may be that in a world where trading decisions are often made by computers, which analyze market data, including news stories, the market was not efficient until the computers had a chance to read the announcement.