Year	Percent
1989	33.83944
1990	30.13039
1991	36.26743
1992	34.61336
1993	27.00717
1994	25.53745
1995	25.43927
1996	23.6677
1997	21.97652
1998	14.96425
1999	14.8304
2000	18.69388
2001	21.94977
2002	20.05057
2003	20.85896
2004	20.90128
2005	20.0775
2006	21.17159
2007	24.16452
2008	25.50125
2009	18.92638
2010	22.61507
2011	24.44472
2012	24.54408
2013	23.1299
2014	22.24075
2015	21.87518
2016	22.83474
2017	23.86231