Year	Percent
1991	31.959
1992	31.956
1993	31.925
1994	31.904
1995	31.303
1996	30.795
1997	30.451
1998	30.259
1999	29.749
2000	30.463
2001	29.591
2002	29.914
2003	29.949
2004	30.677
2005	30.646
2006	31.123
2007	31.103
2008	31.657
2009	31.271
2010	31.098
2011	30.976
2012	30.981
2013	30.683
2014	30.605
2015	29.433
2016	29.259
2017	28.924
2018	28.684
2019	28.498
2020	28.387
2021	28.246
2022	28.174