Year	Percent
1990	6.99669
1991	6.6203
1992	6.48334
1993	6.65464
1994	7.72913
1995	8.98551
1996	8.71991
1997	8.72366
1998	8.63933
1999	8.42251
2000	8.73598
2001	8.80257
2002	8.56058
2003	8.65181
2004	8.97496
2005	9.17945
2006	8.77976
2007	9.77247
2008	10.44009
2009	11.84404
2010	13.39612
2011	13.25974
2012	13.86217
2013	15.29282
2014	15.90398
2015	16.70976
2016	18.73515
2017	21.30181