Year	%
1988	28.09
1989	28.09
1990	19.32
1992	19.33
1993	21.59
1994	20.92
1995	19.41
1996	13.94
1997	12.19
1998	10.05
1999	9.21
2000	7.02
2001	6.71
2002	5.05
2003	4.25
2004	4.98
2005	4.95
2006	4.94
2007	4.86
2008	4.89
2009	4.87
2010	4.87
2011	3.84
2012	3.75
2013	3.72
2015	3.66
2016	4.77
2017	3.57
2018	3.73
2019	3.39
2020	3.25
2021	3.87