Year	Percent
1991	42.788
1992	41.847
1993	41.625
1994	41.722
1995	41.566
1996	42.003
1997	41.002
1998	40.7
1999	40.504
2000	40.673
2001	40.274
2002	40.129
2003	39.307
2004	40.488
2005	39.62
2006	36.777
2007	35.625
2008	34.336
2009	33.442
2010	32.974
2011	32.262
2012	32.028
2013	31.35
2014	30.585
2015	31.784
2016	30.923
2017	30.673
2018	30.177
2019	29.574
2020	28.934
2021	28.341
2022	27.709