Year	Number
1960	3.8062034359431727
1961	4.306930873759476
1962	4.49667437843816
1963	5.245286632021535
1964	3.7056951153049877
1965	3.6619978936991915
1966	3.4977432071581496
1967	3.9099741407622575
1968	3.5378934679147584
1969	4.296843678951738
1970	7.497834000227306
1971	7.665607861214985
1972	5.425278873285728
1973	5.556615890043471
1974	5.350879336568572
1975	2.7740134933888783
1976	2.695656081859485
1977	2.3490987658033315
1978	2.7496004693622638
1979	2.5969342099375186
1980	3.863868063454131
1981	6.241973617679361
1982	6.708300955542848
1983	7.8424158525429855
1984	7.809022930074019
1985	9.206805245334678
1986	9.49985708744207
1987	12.013651517069672
1988	23.60575722194586
1989	44.186203888897246
1990	22.198989748183788
1991	8.441204270434856
1992	5.589496892500264
1993	10.18660927071084
1994	5.9612744743666335
1995	4.4762630878466645
1996	5.281462358650102
1997	3.358833019200734
1998	2.792216884332739
1999	2.05174477550865
2000	2.1940617910353533
2001	2.4268739885422836
2002	2.3919793396938545
2003	2.704197099225316
2004	2.2114505295735367
2005	2.1242377997572004
2006	2.278091396016334
2007	2.7572484158628954
2008	2.952375373061874
2009	3.508628763409642
2010	3.0105373144470353
2011	3.2806036419463784
2012	3.7433553953680456
2013	3.2684598135881173
2014	3.123433695523964
2015	2.9676732260174896
2016	3.308698958866964
2017	2.9296863599370284
2018	3.0745270357501506
2019	2.7561795370975317
2020	2.298291194553461
2021	2.4098840595913447
2022	2.7478192167290993
2023	3.388964264220395