The annual hospital rankings from U.S. News and World Report will now be released a week later than scheduled after errors were discovered in data which affected 12 “data-driven specialty rankings.”

This data had already been used in the rankings released to hospitals on July 11. A public release had been scheduled on August 1, but that’s now been pushed back to August 8 to give U.S. News time to review the data and release corrected rankings to hospitals first.

“While these changes … allow us to better assess hospital care, they are complex to implement and we discovered errors late in the process,” U.S. News said in an email, which was sent to participating hospitals and obtained by STAT News. “We are confident that once correctly implemented these changes will benefit our shared goal of providing patients with better information about their health care.”

Methodology behind this year’s rankings has been revised to better for the socioeconomic status of patients served by a hospital, as well as evaluating “the care of low-income patients, patient safety and hospitals that accept very sick patients from other hospitals.” U.S. News didn’t say whether those changes caused any of the data errors which led to the delay.

In the 2016 report, Mayo Clinic topped the rankings, taking the top spot from Boston’s Massachusetts General Hospital.