Year	Number
1974	6.4671608968111585
1975	3.396697568861682
1976	3.1032661149812375
1977	2.2706639259542936
1978	3.7726928123892614
1979	5.011688098988566
1980	4.278059988421044
1981	2.7691165817000436
1982	3.0141081617237213
1983	2.815496621399907
1984	2.223175172751825
1985	1.9385567902706817
1986	2.4567752868532096
1987	2.469000442948623
1988	2.5449486542469666
1989	3.537153925044264
1990	3.1611868376464045
1991	2.859720296529176
1992	2.982887115267858
1993	2.500582559871424
1994	3.1448971458138724
1995	3.3738047063600853
1996	3.531518393539885
1997	3.4938242835712874
1998	3.7263488222875853
1999	4.9430033345153666
2000	3.769021643914304
2001	4.038352746558409
2002	4.81285966233626
2003	4.627097857704006
2004	4.006884962108525
2005	4.521700253002997
2006	4.784478321067454
2007	4.843029775071769
2008	3.7625646846031633
2009	5.519809844213181
2010	5.1563884472241
2011	4.254540954852843
2012	4.8565621182562255
2013	5.857131961920503
2014	6.2923192897328235
2015	6.679750960973946
2016	6.998362997884509
2017	6.436190874458382
2018	5.30306831659431
2019	5.591866327598405
2020	7.045389116075599
2021	5.871101861784962
2022	4.967585257482615
2023	5.019702924128473