Year	Percent
1987	28.55257
1988	27.2198
1989	31.6633
1990	30.6999
1991	25.10004
1992	23.20001
1993	24.7
1994	21.5
1995	29.5
1996	31.7
1997	28.2
1998	28.1
1999	25.1
2000	22.1
2001	26.5
2002	20.8
2003	19.1
2004	20.7
2005	17.9
2006	19.12908
2007	20.94182
2008	24.5213
2009	25.38075
2010	24.58586
2011	22.79386
2012	23.27935
2013	23.74172
2014	24.15781
2015	23.7109
2016	24.9
2017	24.9