Year	Number
1961	1.9906807183292043
1962	2.2335673261008293
1963	2.540166380897949
1964	2.7895417543681686
1965	3.0338271729787127
1966	3.4057632889841734
1967	4.130679684566279
1968	4.872898562494924
1969	5.625843876581487
1970	6.22820129546587
1971	8.951150504519392
1972	10.612662779518809
1973	11.443642731179057
1974	12.59131522405434
1975	14.067647894808388
1976	15.481219570891724
1977	18.160854997254088
1978	20.469250608004213
1979	23.170871980617214
1980	23.509953700860894
1981	25.64384452956197
1982	28.2743221885988
1983	30.88396873386918
1984	33.832157831045485
1985	37.163568545921486
1986	39.71213335862774
1987	42.74182776262982
1988	46.106970061645015
1989	56.60555677897673
1990	60.44757400938462
1991	65.14272407495925
1992	69.82901675414551
1993	73.50036288487324
1994	77.38071065989848
1995	83.67955234665958
1996	93.27744139108835
1997	102.10332856851134
1998	111.33208185417169
1999	120.76409380338562
2000	129.93226868824954
2001	139.59145485732108
2002	148.66111498952827
2003	158.5053723740449