Year	Percent
1991	29.118
1992	29.976
1993	25.938
1994	25.028
1995	24.109
1996	22.764
1997	22.079
1998	22.898
1999	23.441
2000	26.583
2001	24.507
2002	25.051
2003	23.262
2004	25.53
2005	25.205
2006	24.96
2007	25.278
2008	25.231
2009	23.227
2010	22.951
2011	23.864
2012	22.236
2013	21.559
2014	21.656
2015	21.718
2016	21.527
2017	21.399
2018	21.604
2019	21.393
2020	21.05
2021	20.727
2022	20.438