Year	Percent
1991	23.065
1992	21.108
1993	21.444
1994	19.809
1995	21.836
1996	21.178
1997	22.044
1998	21.548
1999	21.482
2000	21.972
2001	22.384
2002	22.854
2003	22.812
2004	22.941
2005	23.535
2006	24.084
2007	24.714
2008	25.822
2009	26.188
2010	26.022
2011	25.9
2012	26.496
2013	27.004
2014	27.585
2015	27.962
2016	28.625
2017	28.856
2018	29.085
2019	29.463
2020	30.022
2021	30.601
2022	31.193