Year	Number
1977	3.5849752509028994
1978	1.9233084743495705
1979	4.68271336839879
1980	5.485867600344206
1981	2.001272441504511
1982	1.6911245199148097
1983	1.8462066896424743
1984	2.5017628338414695
1985	2.918638880139381
1986	3.9365112910828426
1987	2.489348005602822
1988	1.9769824766474995
1989	3.190418087100653
1990	4.486763606184297
1991	4.033265041106869
1992	1.7892595506210207
1993	2.020876658290772
1994	2.6578231030474924
1995	3.746535879894357
1996	9.187776040792805
1997	15.041763517417543
1998	17.430144405920203
1999	4.157027268962288
2000	7.1781281560621295
2001	6.316026727746387
2002	4.334261731334587
2003	3.4128586900309434
2004	7.724965515958724
2005	8.615055056654201
2006	10.969653547273454
2007	9.228989977301941
2008	7.265921940455999
2009	7.242092535364606
2010	4.634359793478225
2011	3.9293897009205523
2012	5.051037228713386
2013	4.974914785245495
2014	4.038598780072859
2015	3.9368139849640214
2016	5.2949388840991185
2017	6.9236788237253375
2018	5.415919178011565
2019	3.901788623154436
2020	5.178042601093563
2021	5.720292513860491
2022	4.499050052589084