“The common data set for 2017 states that 728 freshmen enrolled this fall. 246, or just under 34%, of those were from the ED rounds. I’m not sure where the 63% number cited by Forbes came from, but the CDS doesn’t back it up.”
One possibility is that a lot of the original 63% of ED admittees turned down Oberlin based on the financial aid offered. That would be consistent with a school facing challenges in its operating budget. As to where the 63% number cited by Forbes came from, perhaps a press release issued by Oberlin when its ED results were announced? If the PR stated the number of ED admittees, Forbes could have just assumed 100% yield on this number and then viewed it as a percentage of the entire class.