Year	Number
1961	5.234817267711529
1962	5.60565048215192
1963	5.928139233414121
1964	6.257166027096942
1965	6.522244357027103
1966	7.1139200190988925
1967	8.043401689333498
1968	8.655124506741736
1969	9.349071019952657
1970	10.044853463332798
1971	11.69418935972266
1972	12.884097353148576
1973	13.447614100399694
1974	14.647564536921463
1975	15.827144315512667
1976	17.2113707351708
1977	19.583346934899442
1978	21.793072395334992
1979	24.14672191007491
1980	24.918291509364128
1981	27.098004177511363
1982	28.842674289480897
1983	31.134832657078768
1984	33.756438466260036
1985	36.09130397967336
1986	38.36713738769727
1987	40.592294297338285
1988	43.365731630069945
1989	48.913850658989425
1990	52.46795252743687
1991	55.45326725115344
1992	68.42904205271705
1993	70.31573162066677
1994	72.37440631514859
1995	75.52158790468513
1996	79.29178709690787
1997	84.08336514203427
1998	86.55686315171353
1999	91.01880277626552