Year	Percent
1988	12.34322
1989	12.70716
1990	12.90406
1991	13.2861
1992	13.3079
1993	12.9711
1994	12.82814
1995	16.40569
1996	17.93868
1997	19.44475
1998	19.82144
1999	21.53759
2000	22.77451
2001	17.39462
2002	18.16863
2003	16.25806
2004	17.40621
2005	16.93751
2006	16.10377
2007	11.52834
2008	11.19787
2009	12.9134
2010	13.69625
2011	13.37658
2012	13.40496
2013	14.05667
2014	13.88158
2015	14.25174
2016	14.28624