:::::::The idea of a party system has been around for well ov er 100 years (Bryce, Ostrogorski, Ford, Merriam).  The idea of numbering them came up in the 1960s.  If you look at citations at google you will see that "1896" and "forth party system" show up in hundreds of booksmostly reference books and textbooks.  The hundreds of thousands of students who take university and high school courses in Am. govt every year have to learn these ideas, and if they're confused by the textbook they come to Wiki for help. So it's standard fare for encyclopedias. I don't worry too much that a reader might be alarmed or damaged by a new idea. I suggest people come to Wiki to learn new ideas and it's the job of the editors to facilitate that.  A new idea will be clear in 30 seconds just by clicking on the link.