Year	Number
1969	7.551313582586851
1970	8.451731223899065
1971	6.4135593220338984
1972	5.518078791149487
1973	4.80648899188876
1974	4.187440744417844
1975	4.290275372088962
1976	5.763493365281971
1977	4.096222813825078
1978	5.2170612471640165
1979	4.256168078559081
1980	4.564899711762782
1981	4.664414479225126
1982	4.759071144752962
1983	5.006807139267815
1984	4.1441960615011455
1985	3.8728542602164473
1986	3.3546658312704483
1987	5.279949241411313
1988	5.658696595901928
1989	7.153444078159754
1990	7.758335205439597
1991	7.216780486048439
1992	8.886097150827421
1993	9.303858109342356
1994	9.867513181104151
1995	10.556956457782817
1996	11.658695177225816
1997	10.867050621208554
1998	8.276910968423573
1999	7.724974965319875
2000	9.914067504391536
2001	11.390971361547138
2002	9.838542052928693
2003	7.905991324041454
2004	6.288089833071222
2005	8.016743211231223
2006	10.979093989228419
2007	12.052758143553387
2008	10.37578043239665
2009	5.932321938262867
2010	6.054112751566508
2011	6.05107610553041
2012	7.872969697699371
2013	8.303481743477823
2014	7.7872264142104175
2015	7.574853247495917
2016	7.36557598649699
2017	5.313529452178313
2018	5.643334034787723
2019	4.776745391738572
2020	3.5154215510447187
2021	3.591595932920059
2022	3.661841931759462