Year	Percent
1989	13.42782
1990	14.38133
1991	16.58354
1992	17.53343
1993	17.44479
1994	17.75591
1995	18.76119
1996	20.61206
1997	20.62511
1998	22.26196
1999	22.46984
2000	16.47707
2001	16.99371
2002	18.38269
2003	20.12014
2004	19.35951
2005	23.22879
2006	26.17545
2007	25.39302
2008	26.94972
2009	25.16309
2010	30.46602
2011	30.81597
2012	32.43664
2013	30.42771
2014	28.815
2015	27.69342
2016	28.75924
2017	30.91248