Hmm, 2 ISBNs in 2nd place -- how many are situations of coupled ISBN-10 and ISBN-13 pairs and how many are "distinct"? The "instance" plot thickens. :-)

John F. Myers, Catalog Librarian
Schaffer Library, Union College
Schenectady NY 12308

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518-388-6623

-----Original Message-----
Roy Tennant wrote:

As requested, numbers from WorldCat, the 1 May 2013 Research snapshot, with 296,589,450 records:

NO. of Recs ISBNs Percent

230402772 0 77.68%
 58861390 2 19.85%
  4269211 4 1.44%
  1659221 1 0.56%
   515674 6 0.17%
   466645 3 0.16%
   151133 8 0.05%
    84572 5 0.03%
    51967 10 0.02%
    33372 12 0.01%

Keep in mind that WorldCat, being the largest library union database in the world, includes a great deal of material that pre-dates the establishment of the ISBN.