Year	Number
1973	8.888443188557641
1974	14.156750816834554
1975	1.7884473945889037
1976	1.3624394417725252
1977	1.2550514921709548
1978	1.5271810244285577
1979	1.5132532384513435
1980	1.8009795123567789
1981	1.9585174234126024
1982	1.5974204746560672
1983	1.6756179125467272
1984	1.8312579762909333
1985	1.7702142679965642
1986	2.124740905806063
1987	2.223244140526972
1988	2.7086956079586764
1989	2.9491166985997546
1990	2.649422052434234
1991	3.8705763532266433
1992	5.71796809495264
1993	10.37975163706438
1994	13.78066461040624
1995	5.314150521566831
1996	3.0938539544212125
1997	4.880345323747738
1998	6.286918923515563
1999	5.257318550384582
2000	3.724135561703548
2001	2.240855666083675
2002	2.6771307205975416
2003	1.8439439700675055
2004	1.8406787269870366
2005	2.1777153897476604
2006	1.5986187042831705
2007	1.4401716406207818
2008	1.788978141114389
2009	1.6321383563796645
2010	1.535675757747212
2011	1.4818637943798352
2012	2.0179649883922823
2013	2.8295223659142112
2014	3.264195991075011
2015	4.152989674867805
2016	4.318572572798529
2017	4.012141120098737
2018	2.9310544620087224
2019	2.8534796468195944