Year	Number
1970	5.8027192415145485
1971	5.169484953330632
1972	5.55631338120317
1973	5.659835292133452
1974	4.947120049262221
1975	4.505457786784481
1976	2.7414437967570042
1977	2.6195575930576673
1978	3.229832159063654
1979	3.7402362882138944
1980	3.7571297398146326
1981	3.2477509593842973
1982	5.472568299281007
1983	3.414028642200018
1984	3.861714285195193
1985	3.153612142097864
1986	4.087220401803079
1987	4.129531906576761
1988	6.789924058389701
1989	7.93821652995636
1990	7.637675663148132
1991	8.097208385442041
1992	5.829168813326463
1993	6.911482858323006
1994	6.694325375516635
1995	6.288706876886768
1996	7.108630240466112
1997	6.551364509368805
1998	6.70015694067121
1999	7.0265286107374125
2000	7.050681992780154
2001	7.059313388745998
2002	5.6800278426920645
2003	6.3605665310550705
2004	5.228165772961794
2005	6.330336634409838
2006	6.1054686161828515
2007	6.191662664123766
2008	6.829972398997122
2009	5.759983493322175
2010	6.436558782385424
2011	6.376590385056495
2012	6.120367610463272
2013	5.039733872075791
2014	4.740391697876658
2015	4.3673614769060904
2016	4.349642224107332
2017	4.6769408673863895
2018	4.3513304597972216
2019	4.21774773471034
2020	3.3571924075109627
2021	3.0678089923168224
2022	3.157935917130492
2023	2.9445952694657676