Public universities with fewer graduate students may not use many TAs because of lack of supply.
Of course, at these schools, and LACs, a significant number of the faculty may be adjuncts.
There are no quick stats that people can cite – and, even if there were, the stats could vary wildly by department (e.g. English and foreign languages commonly use TA as lead instructors in frosh-level courses, but that is much less common in other subjects, where TAs are usually secondary instructors in discussion or lab sections), so that overall school stats can mislead (just like proxy measures of class size). Someone looking for the answer to this question, for a specific school and potential major subject, needs to dig around the school’s class schedule to figure out the class formats, and match up instructor names to rosters of faculty and graduate students in that department.