Year	Percent
1991	33.71347
1992	33.58974
1993	33.43673
1994	33.21761
1995	32.97136
1996	32.70058
1997	32.41475
1998	32.00957
1999	31.54744
2000	31.14636
2001	30.57729
2002	29.99709
2003	29.21417
2004	29.30689
2005	27.91001
2006	27.02772
2007	26.49997
2008	25.7071
2009	25.13303
2010	24.43015
2011	23.77805
2012	23.1931
2013	22.52065
2014	21.79774
2015	21.2311
2016	20.63687
2017	20.08246
2018	19.59112
2019	19.09052