Year	Number
1978	13.235012900563431
1979	15.015616044566586
1980	12.464933085745102
1981	9.207679548257023
1982	8.84440433530697
1983	9.16466383110789
1984	7.454362259000106
1985	8.569061995083766
1986	11.347864689755012
1987	11.684284888231664
1988	10.300846967275744
1989	8.801173284566838
1990	7.747667024804806
1991	5.602094308645513
1992	4.914208102034428
1993	5.161471857209331
1994	4.852509210139591
1995	5.181589984506058
1996	4.910775874812121
1997	4.839047551628068
1998	5.866330508422794
1999	6.417137412157739
2000	6.615078262094985
2001	8.046297184082375
2002	3.26634060517241
2003	7.227974434472796
2004	6.361576285347714
2005	6.424411672764048
2006	5.2628647507234305
2007	6.048800046978267
2008	6.356442432642975
2009	9.88019940610582
2010	7.627399423501824
2011	8.301810035985346
2012	7.468176482434923
2013	8.877729660912216
2014	9.685591745310091
2015	10.536506073360071
2016	10.0260447313037
2017	10.357367251210244
2018	9.673090740995757
2019	9.613842599010745
2020	12.93496217368766
2021	9.132495873205913
2022	6.734222748023738
2023	7.4313307843080185