Year	Percent
1983	23.8957
1984	28.6801
1985	28.7912
1986	26.447
1987	27.0535
1988	25.304
1989	23.0484
1990	23.0401
1991	22.6234
1992	24.9791
1993	27.6583
1994	30.4954
1995	30.6397
1996	30.2919
1997	31.1386
1998	28.4245
1999	28.2043
2000	22.5593
2001	20.467
2002	20.7931
2003	18.173
2004	19.7684
2005	21.2845
2006	22.5239
2007	19.4552
2008	18.0741
2009	21.6432
2010	23.021
2011	22.6382
2012	23.122
2013	24.384
2014	23.1323
2015	23.3356
2016	24.0794
2017	21.2522