Year	Percent
1991	39.02074
1992	38.45918
1993	35.29353
1994	35.17703
1995	33.9934
1996	32.71743
1997	31.37729
1998	29.80298
1999	28.70284
2000	29.62993
2001	28.54286
2002	27.52275
2003	29.87009
2004	31.83339
2005	30.93967
2006	31.2287
2007	31.75763
2008	31.6921
2009	29.95797
2010	28.2764
2011	29.23912
2012	27.07137
2013	27.9588
2014	27.55276
2015	25.8151
2016	25.57364
2017	25.04452
2018	21.66345
2019	20.59692