Year	% of total
1971	5.435610661493513
1972	5.267515613889327
1973	5.001647802468566
1974	5.486359005245188
1975	5.036194935680062
1976	4.416196900440643
1977	5.2987144013092395
1978	4.76712498370332
1979	5.62237529573566
1980	5.553629001443791
1981	5.381442297917182
1982	6.1170128545394356
1983	5.482814841478614
1984	5.169277105046017
1985	5.534866387879201
1986	6.0342583408022294
1987	6.559057786427802
1988	6.589348683602789
1989	7.454059796128224
1990	8.434311114324826
1991	8.977479855917395
1992	9.564679680845972
1993	9.649615821653502
1994	9.601740476331683
1995	10.79586160950071
1996	11.060701032838903
1997	11.775663430504698
1998	13.489709398111884
1999	14.199600808017626
2000	13.719519068029415
2001	13.847766242449639
2002	14.776369642171119
2003	16.86334870642797
2004	17.535504756996136
2005	16.446214998596467
2006	15.393586636597128
2007	16.053380941962356
2008	14.780431994595949
2009	16.606966002443823
2010	15.529158480782954
2011	14.51333549557439
2012	11.8445487534365
2013	9.67736573135087
2014	9.019151263786537
2015	9.100102039169263