Year	Number
1974	13.70305
1975	13.79207
1976	13.89587
1977	14.03912
1978	14.10798
1979	14.34038
1980	14.62528
1981	15.21292
1982	15.50314
1983	15.97124
1984	16.12386
1985	16.33117
1986	16.70826
1987	16.4049
1988	17.16614
1989	17.62049
1990	17.43369
1991	18.64358
1992	20.38354