Year	Percent
1991	32.744
1992	33.352
1993	34.025
1994	33.227
1995	31.924
1996	31.857
1997	33.129
1998	34.437
1999	34.603
2000	34.322
2001	32.764
2002	31.559
2003	30.017
2004	29.969
2005	31.899
2006	32.456
2007	32.566
2008	31.608
2009	30.125
2010	30.223
2011	29.888
2012	30.472
2013	29.672
2014	28.662
2015	28.516
2016	28.616
2017	28.904
2018	28.993
2019	29.083
2020	29.043
2021	28.989
2022	28.918