1978 1980 1985 1988 1990 1992 1995 1996 1997 | 19.4 16.7 12.9 15.89 12.608 22.866 25.641 25.767 28.313 | 34.2 28.43 22.5 27.96 39.14 39.45 44.7 43.68 49.21 | 18.5 14.09 11.45 13.68 18.1 19.81 23.43 29.635 26.519 | 2.38 4.25 6.45 7.3 7.914 9.17 9.009 9.933 11.437 |