Year	Percent
1991	48.113
1992	47.283
1993	46.325
1994	45.336
1995	44.379
1996	43.644
1997	43.083
1998	42.594
1999	42.042
2000	41.109
2001	40.16
2002	39.188
2003	38.197
2004	37.196
2005	36.187
2006	35.856
2007	35.72
2008	35.635
2009	34.586
2010	34.188
2011	33.624
2012	32.763
2013	31.736
2014	30.737
2015	29.862
2016	29.023
2017	28.94
2018	28.892
2019	28.837
2020	28.745
2021	28.63
2022	28.482