Year	Percent
1988	12.04418
1989	10.643
1990	11.43579
1991	10.91669
1992	12.41331
1993	14.69706
1994	14.57736
1995	13.53546
1996	14.09728
1997	14.56198
1998	15.67879
1999	15.68283
2000	16.76367
2001	18.19218
2002	20.63672
2003	16.83238
2004	17.43591
2005	16.09433
2006	17.21787
2007	14.72975
2008	14.84988
2009	15.80276
2010	16.15029
2011	18.46185
2012	18.82919
2013	19.14261
2014	20.73798
2015	20.51992
2016	19.28457