Year	Percent
1991	34.824
1992	34.798
1993	32.935
1994	31.634
1995	32.148
1996	31.274
1997	30.443
1998	29.962
1999	28.466
2000	28.329
2001	28.126
2002	27.151
2003	26.571
2004	25.726
2005	25.967
2006	25.765
2007	26.034
2008	25.874
2009	24.047
2010	28.195
2011	27.631
2012	28.341
2013	28.063
2014	29.979
2015	32.195
2016	28.296
2017	28.641
2018	28.728
2019	28.758
2020	28.71
2021	28.639
2022	28.528