Year	Number
1974	4.257651267055803
1975	4.174490776706818
1976	6.010609825042214
1977	5.782178680036752
1978	5.349576291662172
1979	5.231471443618397
1980	4.5733615712325335
1981	3.691851100372744
1982	3.2455076688805904
1983	2.845493661015995
1984	2.5748697794968765
1985	3.705807789103999
1986	5.096751803196333
1987	5.565295861150093
1988	3.944082567521826
1989	3.6590877274816256
1990	3.6044141151063767
1991	3.211268414880915
1992	4.435743332992921
1993	5.837487844022353
1994	4.31341404796642
1995	3.165888364761105
1996	3.412102565227199
1997	2.571889811210492
1998	4.315645955255738
1999	4.437743926725848
2000	3.310322610086367
2001	3.7791037256846454
2002	4.035129814636163
2003	5.007262129418004
2004	6.16483766943988
2005	5.943001358137106
2006	6.2040707745539745
2007	6.704203767712405
2008	5.589263215446472
2009	7.24461462096016
2010	6.3411520985842165
2011	6.915595438696217
2012	6.963827820048536
2013	6.667252439109093
2014	5.67002202010291
2015	5.507770410748159
2016	5.642709978275123
2017	5.507607411304222
2018	4.910236915543464
2019	5.265751259437741
2020	6.268809973790888
2021	5.186206096193104
2022	4.330752566885675