Year	Percent
1990	19.35399
1991	22.89556
1992	19.94673
1993	19.76435
1994	19.34459
1995	20.71788
1996	23.381
1997	27.11448
1998	30.67852
1999	29.89706
2000	33.56175
2001	30.84535
2002	32.16624
2003	36.04601
2004	36.94835
2005	35.66526
2006	39.92741
2007	42.09741
2008	42.89747
2009	38.04146
2010	42.0532
2011	44.51955
2012	44.88387
2013	44.37203
2014	46.14573
2015	46.42646
2016	48.21253
2017	49.39794