Year	Number
1980	0.08004096331085236
1981	0.9048437606136099
1982	1.792672007757584
1983	2.351611945313075
1984	2.0073246328154717
1985	0.8413643420926862
1986	0.6609270290145752
1987	0.9204699661972007
1988	0.754678329561331
1989	0.1993354098201464
1990	0.7190204336892979
1991	1.0163325030993418
1992	1.494973487137515
1993	2.0990507837538903
1994	3.1571113338159833
1995	3.435322333641452
1996	3.6424670899004217
1997	4.301638917786462
1998	4.45394491915705
1999	5.8297608842989455
2000	6.160424819339245
2001	7.155155649726742
2002	6.655684336348521
2003	7.464501427350876
2004	7.02241146346562
2005	6.101832198138878
2006	6.610516720011346
2007	7.203643162218026
2008	4.859733968499441
2009	6.372568189312861
2010	4.995730890273896
2011	3.9868997528571057
2012	4.591114633119757
2013	4.994308493905351
2014	4.756757794938952
2015	4.487745816313333
2016	5.205849234238662
2017	5.492016408053734
2018	4.141863501048362