"The Catholic Church is the religion with the greatest percentage loss of membership with this trend: 10.3%"

Still, if one calculates on a graph from 1960 to the present, Protestant Churches as a whole have the greatest percentage loss of membership: -20%. In 1960, more than 65% of the nation was Protestant. Today, according to the PRII study, less than 45% identify as Protestant (including all denominations). According to that same study, Catholicism (21%) is nearly 33% of American Christianity because of the drop of Protestantism.