John Bear, co-author of Degree Mills, a book that delves into the topic of fake degrees in higher education has claimed that more than half of all new PhDs in the United States are issued from diploma mills.
I found him quoted in a couple of sources:
"Diploma mills have been around for more than 700 years, and things are worse now than they've ever been," said John Bear, co-author of "Degree Mills: The Billion-Dollar Industry That Has Sold Over a Million Fake Diplomas." He added: "Just two of the sellers -- Axact from Pakistan and University Degree Program (UDP) run by an American in Romania -- have accounted for many hundreds of thousands of sales to Americans, and that's just the tip of the iceberg. More than half of all new PhDs in the U.S. each year are fake."
He is similarly quoted (but misattributed) in Inside Higher Ed.
I have not seen any substantial evidence to support the claim. By itself, it seems difficult to believe, considering the long process of PhD recognition in the United States.
Is this statistic true?