Daily Digit is the story behind the numbers that make our world work. Today we're looking at the lives of nonhuman Americans — aka pets. Sixty-eight percent of Americans have pets, and while dogs and cats are by far the most common companion animals, there are plenty of options. In some states it's even legal to own primates (though animal rights advocates largely oppose the practice). From necessities like food, medical care, and collars to luxuries like kitten couture and diamond-encrusted dog tags, Americans spend $68.5 billion on their pets annually. Does that seem excessive?