Year	Number
1961	5.093087807189764
1962	5.369544131910766
1963	5.797401436304092
1964	6.454408256657416
1965	7.126920299049367
1966	9.846177978647267
1967	12.357113304568829
1968	15.402021241846239
1969	17.97617390266701
1970	12.6355341920913
1971	15.183672240399865
1972	19.282040939800343
1973	23.863339311225264
1974	28.43921900501723
1975	35.463767819524264
1976	40.87463757385398
1977	48.15409934264007
1978	57.563489369580644
1979	68.97999124456004
1980	77.14365284840483
1981	81.68889481183815
1982	79.8298682284041
1983	78.4736837234269
1984	75.130551488531
1985	71.28431331981628
1986	72.30407523510972
1987	73.70340658159172
1988	72.44382854135141
1989	69.82333219406604
1990	66.20391867031915
1991	63.380700147357516
1992	62.36779916155453
1993	60.212289678244616
1994	58.154557365701706
1995	56.98903804248382
1996	57.027968531235416
1997	58.74766312192289
1998	61.71174069447288
1999	66.72580163324483
2000	82.65831564521251