Year	Percent
1988	10.79142
1989	12.05035
1990	13.75594
1991	15.91473
1992	14.8963
1993	13.93698
1994	13.81223
1995	14.98593
1996	15.82917
1997	15.54943
1998	15.55952
1999	14.95138
2000	17.72943
2001	15.69731
2002	14.19283
2003	13.72987
2004	12.09374
2005	13.08441
2006	13.345
2007	12.75222
2008	13.60045
2009	16.25767
2010	14.04658
2011	13.42582
2012	13.7835
2013	14.01185
2014	13.56094
2015	13.83882
2016	12.93471