Year	Percent
1990	4.494
1991	7.418
1992	11.148
1993	19.259
1994	19.923
1995	18.3666
1996	20.5586
1997	20.9625
1998	16.8146
1999	15.4022
2000	8.0724
2001	10.5983
2002	12.4235
2003	13.1329
2004	17.1861
2005	21.8094
2006	22.0413
2007	19.7736
2008	20.7178
2009	23.746
2010	23.6468
2011	22.2776
2012	22.2247
2013	22.2966
2014	21.4762
2015	19.5689
2016	17.2896
2017	16.9835