CREATE TABLE table_73407 ("District" TEXT, "Vacator" TEXT, "Reason for change" TEXT, "Successor" TEXT, "Date successor seated" TEXT)

Name the reason for change pennsylvania 13th
SELECT "Reason for change" FROM table_73407 WHERE "District" = 'Pennsylvania 13th'
SELECT "Reason for change" FROM "table_73407" WHERE "District" = 'Pennsylvania 13th'