Name the total number of rank for percentage change yoy 13.1%
CREATE TABLE "universities_and_colleges_ranked_by_endo" (
  "state_rank" real,
  "national_rank" real,
  "institution" text,
  "location" text,
  "public_or_private" text,
  "endowment_funds" text,
  "percentage_change_yoy" text
);
SELECT COUNT("national_rank") FROM "universities_and_colleges_ranked_by_endo" WHERE "percentage_change_yoy"='13.1%';