Year	Percent
1991	39.17649
1992	40.05527
1993	42.12445
1994	42.18556
1995	42.08137
1996	40.20516
1997	41.17327
1998	40.37596
1999	39.81909
2000	43.01964
2001	44.97221
2002	43.27733
2003	43.24333
2004	62.75015
2005	41.40497
2006	40.23919
2007	40.95226
2008	24.1687
2009	20.77868
2010	17.99134
2011	24.49882
2012	24.76478
2013	24.14308
2014	23.83465
2015	23.26826
2016	22.89687
2017	22.51524