• For every human born, 7 puppies and kittens are born.
  
  
• One female cat and her offspring can produce 420,000 cats in 7 years.
  
  
• One female dog and her offspring can produce 67,000 dogs in 6 years.
  
  
• An estimated 6 to 8 million dogs and cats are euthanized in shelters each year. Millions more are abandoned, only to suffer from illness or injury before dying.
  
  
• In a study of relinquishment of dogs and cats in 12 U.S. animal shelters, 30% of the surrendered dogs were purebreds.
  
  
• The same study indicated that 55% of the surrendered dogs and 47% of the surrendered cats were unaltered.
  
  
• It costs U.S. taxpayers an estimated $2 billion each year to round up, house, euthanize and dispose of homeless animals.
  
  
• Approximately 55% of dogs and puppies entering shelter are killed, based on reports from 1,038 facilities across America.
  
  
• Approximately 71% of cats and kittens entering shelter are killed, based on reports from 1,038 facilities across America.
  

Some Statistics are from the National Human Education Society, Humane Society of the United States, and the SPCA and various related articles.