Year	Percent
1991	60.33399
1992	60.90455
1993	56.77261
1994	55.98793
1995	51.97513
1996	50.05998
1997	50.35009
1998	51.26546
1999	48.52436
2000	48.78958
2001	46.04305
2002	43.84544
2003	41.63644
2004	39.29023
2005	38.67597
2006	39.78224
2007	39.53105
2008	39.75101
2009	38.99148
2010	38.2445
2011	41.0046
2012	42.14214
2013	41.75317
2014	33.43903
2015	32.2808
2016	31.1642
2017	31.45707
2018	32.13636
2019	31.42243