Year	% of total
1990	73.15617399404151
1991	72.53780555963837
1992	70.30948485299223
1993	68.54741331502916
1994	68.26757010381984
1995	67.45604906021471
1996	68.40005389013504
1997	67.4925045668732
1998	67.69819012356737
1999	66.19151661980229
2000	65.89824157869997
2001	64.61707819230817
2002	65.38312763124753
2003	66.19167301012328
2004	65.19128298051952
2005	65.71235723995673
2006	66.40418970383301
2007	66.41618947719506
2008	68.09205426263276
2009	65.52116317945143
2010	67.11864308629536
2011	67.44589986144362
2012	67.50446314596381
2013	66.15518883044359
2014	66.01329338352475
2015	65.48122553661098