Year	Percent
1991	30.734
1992	30.561
1993	30.438
1994	30.283
1995	30.115
1996	29.991
1997	29.754
1998	29.485
1999	29.277
2000	29.078
2001	29.137
2002	28.888
2003	28.679
2004	28.506
2005	28.588
2006	28.324
2007	28.015
2008	27.998
2009	28.256
2010	28.119
2011	27.985
2012	27.964
2013	27.933
2014	27.939
2015	27.882
2016	27.833
2017	27.829
2018	27.813
2019	27.796
2020	27.781
2021	27.766
2022	27.751