I found worldwide ISO certificate data in a press release from the International Organization for Standardization ( http://www.iso.ch ) under their News category. The item is called The ISO Survey of ISO 9000 and ISO 14000 Certificates: Seventh cycle -- 1997 (ISBN 92-67-10284-2).
For the period January 1993 through the end of 1997, there were 18,581 ISO 9000 certifications in the USA (Annex A of the report).
For the same period, there were 334 ISO 9000 certificates withdrawn in the USA (section 3.7 of the report). The survey states that the certificates were withdrawn "for a variety of reasons."
That represents less than 2%
I would imagine that "a variety of reasons" would include companies that voluntarily decide they no longer want to participate as well as companies that go out of business.
The world-wide registration withdrawals are also less than 2%.