Year	Percent
1985	27.35043
1986	28.88147
1987	28.36237
1988	23.96239
1989	22.9381
1990	22.67429
1991	23.79444
1992	27.2636
1993	28.90031
1994	28.86845
1995	28.75592
1996	29.72989
1997	32.07513
1998	32.49127
1999	34.49475
2000	36.73078
2001	38.12942
2002	38.48668
2003	39.47001
2004	40.20875
2005	38.13114
2006	38.58473
2007	38.51162
2008	37.0777
2009	37.38819
2010	32.13189
2011	32.24441
2012	33.55779
2013	33.19004
2014	33.21439
2015	33.25008
2016	32.71504
2017	33.33897