Year	Number
1961	0.5433455433455433
1962	0.6329884357881923
1963	0.9101941747572815
1964	1.2099213551119177
1965	1.5078407720144753
1966	1.8050541516245486
1967	2.697841726618705
1968	2.937649880095923
1969	3.1774580335731413
1970	3.317811408614668
1971	3.5506402793946448
1972	3.783469150174622
1973	4.016298020954599
1974	4.072398190045249
1975	4.125412541254125
1976	3.817550818046604
1977	3.9205955334987594
1978	4.01985111662531
1979	4.129353233830846
1980	4.477611940298507
1981	4.967709885742673
1982	5.46448087431694
1983	5.961251862891207
1984	6.458022851465474
1985	6.886374815543532
1986	7.367387033398821
1987	7.858546168958743
1988	8.52411105698977
1989	9.254749147588894
1990	10.228933268387726
1991	10.664081434803684
1992	10.633379565418402
1993	7.8431372549019605
1994	7.753164556962025
1995	7.577583609520939
1996	5.286343612334802
1997	4.961411245865491
1998	4.746136865342163
1999	4.424778761061947
2000	4.218889883616831
2001	3.888888888888889
2002	3.493877551020408
2003	1.141029956243689
2004	1.399440223910436
2005	1.3260753167945742
2006	2.201867183371499
2007	2.2382920110192837