Analysts are no longer allowed to provide confidential sales data from the NPD Group, the tracker has said.
The firm says analysts are not to discuss sales numbers with media or reporters in interviews, emails, notes and in other cases, may have to remove the media from mailing lists.
Analyst firms, such as Wedbush Morgan, have provided a select amount of information on sales figures not reported publicly by NPD recently.
NPD decided last year to stop reporting on sales numbers for software and hardware.
NPD said recently it would look into providing digital sales data in reports in the future.