Year	Percent
1991	43.915
1992	42.998
1993	40.263
1994	40.202
1995	39.371
1996	37.395
1997	37.08
1998	35.913
1999	35.728
2000	35.389
2001	32.521
2002	30.816
2003	29.003
2004	29.126
2005	28.498
2006	27.618
2007	27.279
2008	26.332
2009	23.112
2010	24.192
2011	24.498
2012	25.151
2013	26.476
2014	26.815
2015	28.153
2016	28.048
2017	28.077
2018	28.058
2019	27.795
2020	27.717
2021	27.591
2022	27.407