Year	Percent
1988	16.68
1989	16.3
1990	16.02
1991	15.35
1992	16.29
1993	17.75
1994	16.04
1995	15.55
1996	13.5
1997	14.35
1998	14.16
1999	15.02
2000	13.05
2001	16.21
2002	19.16
2003	20.53
2004	20.56
2005	19.88
2006	16.43
2007	17.24
2008	18.47
2009	22.78
2010	19.74
2011	16.73
2012	15.68
2013	16.94
2014	17.83
2015	18.48
2016	19.48
2017	20.52
2018	20.16
2019	25.23
2020	25.09