Year	Percent
1986	14.42404
1987	13.56098
1988	17.84436
1989	14.63069
1990	12.56584
1991	15.07033
1992	17.64014
1993	24.2553
1994	25.47582
1995	27.14424
1996	28.1029
1997	28.29958
1998	29.04988
1999	27.62976
2000	29.60991
2001	31.17277
2002	33.22053
2003	35.44486
2004	35.46533
2005	33.7574
2006	34.53665
2007	39.56627
2008	36.49312
2009	37.16256
2010	35.69381
2011	29.75064
2012	27.24332
2013	26.67562
2014	26.83267
2015	27.67673
2016	26.57806
2017	25.76843