Iowa State University Veterinarian Records, RS 22/6/0/9, University Archives, Special Collections Department, Iowa State University, http://www.add.lib.iastate.edu/spcl/arch/rgrp/22-6-0-9.html
Conservative estimates indicate that there are between 65 and 110 million cats and dogs in the U.S. today and that about 200,000,000 are born annually (2,000-10,000 per hour). To provide a home for every dog and cat, each household would need to own 30 pets. This overpopulation of companion animals warrants investigation in four specific areas.
Higgins, Tonya and Pineda, Mauricio
"Pet Population Control,"
Iowa State University Veterinarian: Vol. 42
, Article 11.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol42/iss2/11