Year	Percent
1991	35.916
1992	35.007
1993	31.391
1994	28.736
1995	29.385
1996	29.381
1997	28.18
1998	28.988
1999	30.719
2000	32.562
2001	33.423
2002	33.768
2003	34.211
2004	32.822
2005	34.44
2006	34.246
2007	35.128
2008	35.251
2009	33.288
2010	33.713
2011	32.935
2012	31.241
2013	31.294
2014	30.625
2015	30.472
2016	30.583
2017	31.433
2018	32.14
2019	32.477
2020	32.839
2021	33.175
2022	33.498