Year	Percent
1991	41.11
1992	40.937
1993	38.309
1994	37.638
1995	34.613
1996	32.988
1997	34.665
1998	34.368
1999	32.252
2000	31.073
2001	29.706
2002	27.249
2003	28.839
2004	30.778
2005	31.785
2006	32.528
2007	33.6
2008	33.283
2009	32.502
2010	32.564
2011	33.426
2012	33.173
2013	33.984
2014	34.795
2015	34.31
2016	34.078
2017	33.641
2018	33.545
2019	33.442
2020	33.346
2021	33.274
2022	33.216