Year	%
1988	27.57
1989	33.85
1990	33.33
1992	32.31
1993	23.36
1994	28.38
1995	22.36
1996	14.35
1997	16.48
1998	17.5
1999	17.35
2000	17.05
2001	15.31
2002	16.62
2003	14.5
2004	13.24
2005	11.45
2006	10.87
2007	9.97
2008	9.5
2009	9.49
2010	9.36
2011	9.33
2012	8.36
2013	8.17
2014	8.74
2015	7.61
2016	8.27
2017	6.84