Year	Percent
1988	13.98078
1989	11.58756
1990	12.53194
1991	15.57777
1992	16.70434
1993	16.56377
1994	14.3712
1995	15.244
1996	16.23722
1997	19.63197
1998	23.60651
1999	18.77185
2000	18.14348
2001	14.26844
2002	16.29467
2003	13.23207
2004	11.0217
2005	14.25362
2006	13.86533
2007	15.18665
2008	17.55274
2009	16.97126
2010	17.00702
2011	19.81555
2012	17.67299
2013	19.01773
2014	21.0338
2015	20.28128
2016	21.05736
2017	22.22029