Year	%
1989	42.92
1990	33.5
1991	16.78
1992	14.66
1993	13.37
1994	11.86
1995	11.96
1996	13.29
1997	12.27
1998	12.23
1999	13.12
2000	12.71
2001	11.77
2002	11.44
2003	11.19
2004	9.66
2005	9.34
2006	8.98
2007	8.55
2008	8
2009	7.84
2010	8.87
2011	8.39
2012	8.07
2013	8.33
2014	7.35
2015	7.71
2016	8.9
2017	6.98