Year	Percent
1988	23.9288
1989	24.55742
1990	24.2405
1991	24.24647
1992	24.06979
1993	24.59316
1994	25.54594
1995	26.54654
1996	26.14833
1997	26.40513
1998	26.15223
1999	26.64937
2000	28.68867
2001	26.5955
2002	24.77556
2003	24.42805
2004	24.10432
2005	22.98115
2006	22.05696
2007	18.40781
2008	17.31434
2009	18.75847
2010	17.97278
2011	17.45941
2012	17.40479
2013	16.78429
2014	16.68882
2015	16.78206
2016	16.22075