Year	Percent
1991	39.186
1992	37.82
1993	34.637
1994	31.647
1995	31.148
1996	31.625
1997	31.03
1998	29.945
1999	25.612
2000	25.701
2001	26.917
2002	25.241
2003	24.762
2004	24.342
2005	25.751
2006	27.386
2007	29.861
2008	31.773
2009	31.147
2010	30.486
2011	29.498
2012	29.194
2013	28.705
2014	30.148
2015	30.746
2016	33.224
2017	34.029
2018	34.177
2019	33.497
2020	32.805
2021	31.974
2022	31.016