Here is another Mcardle article on how people who don't pay their own medical bills do not add on to the rising cost of healthcare. She uses a graph by AEI to show the level of Veterinary care people pay for their pets is commiserate with the what the country spends on healthcare. both of which rise at same rate.
the graph is a gross total expenditures for pets and people health care and not per capata, or doesn't account for the fact there are more people than in 1984 with steady population growth. Maybe I'm reading it wrong, but wouldn't more people also mean more pets and vet visits overall during this time frame and account for the lineal correlation?