Year	Number
1980	3.0294398675713836
1981	3.911133330235436
1982	3.69282165571461
1983	3.0233461083838726
1984	3.603204624575204
1985	3.2400910151087277
1986	2.6019579608604877
1987	2.877707771299165
1988	3.91503418502749
1989	4.447109100863684
1990	3.3490739267924847
1991	2.176316327897435
1992	1.7021102329847932
1993	1.1325659360767366
1994	0.783769280509777
1995	0.6873845231744665
1996	0.6737909491082366
1997	0.5811238908480106
1998	0.5563753511547518
1999	0.5497458829076801
2000	0.5864985686412493
2001	0.5988932685843692
2002	0.5061763799172242
2003	0.659863912753057
2004	0.7333031323077842
2005	0.7853422109572774
2006	0.7868081076713668
2007	0.5777163862821334
2008	0.6084649796933381
2009	0.41428915687921863
2010	0.5932904295917455
2011	1.0148502551247494
2012	0.870952990282196
2013	0.8467029096977328
2014	0.7672855552448502
2015	0.796356490091246
2016	0.7086490253632536
2017	1.3815439344535667
2018	1.3899186999063353
2019	1.0903720958948422