Year	Percent
1991	29.432
1992	28.909
1993	28.792
1994	28.299
1995	27.695
1996	26.922
1997	26.276
1998	26.091
1999	25.835
2000	25.531
2001	25.508
2002	25.808
2003	26.044
2004	26.153
2005	26.496
2006	26.284
2007	25.954
2008	25.77
2009	25.813
2010	25.785
2011	25.309
2012	24.932
2013	24.784
2014	24.643
2015	24.608
2016	23.968
2017	23.357
2018	22.905
2019	22.605
2020	22.404
2021	22.038
2022	21.723