Year	Percent
1991	28.666
1992	26.141
1993	28.993
1994	30.181
1995	29.694
1996	31.579
1997	33.302
1998	35.449
1999	34.152
2000	32.988
2001	31.826
2002	31.333
2003	30.351
2004	29.893
2005	27.975
2006	28.13
2007	27.001
2008	25.244
2009	22.544
2010	21.1
2011	20.812
2012	21.216
2013	20.724
2014	20.354
2015	20.926
2016	21.284
2017	21.761
2018	21.942
2019	21.856
2020	21.628
2021	21.413
2022	21.158