Year	Number
1960	1.1474963751390572
1961	1.2225794767323852
1962	1.1523001821941963
1963	1.2084371884724157
1964	1.183198460352574
1965	1.9058130427882571
1966	1.8249742129960385
1967	2.01968125349915
1968	2.163702788510849
1969	2.2602934319825243
1970	2.3681104376383786
1971	2.191741575566469
1972	2.373414871346741
1973	2.512832105565481
1974	3.0611204421729603
1975	3.921284557332878
1976	2.9989567183438153
1977	3.068956170412717
1978	3.2647746066903762
1979	3.130971725707953
1980	3.4313966836301475
1981	4.450583578903656
1982	5.311704824192453
1983	6.4395814795452555
1984	7.802849399666361
1985	6.327628170657167
1986	5.623520646791891
1987	4.768331016068731
1988	5.701460081969941
1989	5.759661217764508
1990	2.658992477313423
1991	2.7812104953025996
1992	3.355686669822003
1993	2.682986835451166
1994	3.1398469659693005
1995	4.152835789866679
1996	4.343653755067566
1997	5.8459450343821375
1998	3.4425988161703325
1999	3.380844728274476
2000	4.016581962157759
2001	4.3044345157617325
2002	3.9758059068532945
2003	3.2906910902090556
2004	2.474777251141529
2005	2.545715546253822
2006	2.539010695078285
2007	2.375893066010687
2008	2.994887441236961
2009	2.9106622526564854
2010	3.103562801145641
2011	2.986630504719028
2012	3.078564680240428
2013	3.3583452336219
2014	3.997076448539345
2015	4.20055065939016
2016	4.099940997665245
2017	3.8167962118502943
2018	4.423402936148293
2019	4.331085420007016
2020	4.297794277529678
2021	4.237602284680393
2022	4.230526024919361
2023	4.36710578898349