Year	% of total
1971	0
1972	0
1973	0
1974	0
1975	0
1976	0
1977	0
1978	0
1979	0
1980	0
1981	1.799111884203923
1982	1.8004590665052518
1983	1.8938924065903477
1984	1.5464197929783006
1985	2.1626588296593128
1986	2.0062648273428842
1987	2.8538934433899623
1988	2.51883201774108
1989	3.0223242963813215
1990	3.117031652575559
1991	3.531911821416489
1992	3.807405339824831
1993	4.164783048872756
1994	3.640112016392362
1995	2.533886634506747
1996	1.604511285300745
1997	1.663910364480746
1998	2.337541081788632
1999	2.4165758893068734
2000	2.724089445256439
2001	2.777329960237452
2002	2.8670032564530783
2003	2.483553202146415
2004	2.1758251348076056
2005	3.619169093955083
2006	3.8633723750351554
2007	3.161855678026964
2008	3.5173524871572033
2009	2.741901201676037
2010	2.891750884858019
2011	2.96895877174228
2012	2.714218098232336
2013	2.9817527076781594
2014	4.103633720139475
2015	4.548870160634386