Year	Percent
1991	36.512
1992	35.484
1993	32.807
1994	30.089
1995	27.38
1996	26.293
1997	25.342
1998	24.421
1999	23.248
2000	24.265
2001	23.523
2002	22.951
2003	22.941
2004	22.379
2005	21.823
2006	20.983
2007	20.757
2008	20.489
2009	19.01
2010	20.117
2011	21.599
2012	22.072
2013	21.894
2014	21.866
2015	20.615
2016	21.348
2017	21.234
2018	21.031
2019	20.724
2020	20.35
2021	20.019
2022	19.726