Year	Number
1961	0.8715862870424171
1962	0.9305571711061997
1963	0.9877977919814062
1964	1.0416666666666665
1965	1.0823743876039649
1966	1.1366219595362583
1967	1.2439217460137961
1968	1.472420432665081
1969	1.70261066969353
1970	2.344687111010524
1971	2.56874504922485
1972	2.7044782656301325
1973	2.9131529952907678
1974	3.1321870550870665
1975	3.335520559930009
1976	3.5565769314948565
1977	3.782718212682072
1978	3.8356164383561646
1979	3.8385610879578853
1980	3.837298541826554
1981	3.6776814139861678
1982	3.5149384885764503
1983	3.383210474199582
1984	3.211758301578661
1985	3.0594405594405596
1986	2.9472764981988866
1987	2.7937195452084462
1988	2.568942015308797
1989	2.4076206427300324
1990	2.305414551607445
1991	2.1843367075119873
1992	2.236032059472645
1993	2.1161533035504347
1994	1.9921503330161752
1995	1.8443598286530225
1996	1.6752423118343902
1997	1.5494636471990464
1998	1.4194464158977997
1999	1.2802275960170697
2000	1.1976047904191618
2001	1.0839455618451161
2002	0.9693444807948626
2003	0.8507535245503159
2004	0.5526218838265995
2005	1.9656174946277336
2006	3.807106598984772