(73.8) (73.9) (74.7) (75.4) (76.1) (77.2) (78.4) (79) (78.3) (77.4) (75.9) (73.9) (76.2) Average 17.5 17.3 17.7 18 18.6 19.1 19.7 19.9 19.6 19.4 18.7 17.9 18.6