Year	Percent
1988	14.59319
1989	15.87208
1990	16.46066
1991	17.61854
1992	19.37846
1993	23.38792
1994	22.42544
1995	24.14475
1996	26.77689
1997	27.37786
1998	30.24555
1999	33.28088
2000	35.80657
2001	32.71386
2002	28.01292
2003	31.35063
2004	30.46736
2005	30.88972
2006	28.99002
2007	23.30734
2008	19.24875
2009	20.90427
2010	21.29412
2011	19.8142
2012	20.04515
2013	20.40625
2014	19.90184
2015	19.3236
2016	17.77787