Year	Percent
1991	24.958
1992	26.615
1993	23.167
1994	23.728
1995	21.006
1996	23.85
1997	21.845
1998	19.34
1999	33.216
2000	35.079
2001	30.856
2002	26.724
2003	27.96
2004	23.476
2005	22.972
2006	23.065
2007	22.203
2008	21.21
2009	21.237
2010	24.331
2011	22.708
2012	24.092
2013	22.699
2014	22.369
2015	21.183
2016	20.739
2017	20.723
2018	20.154
2019	20.062
2020	19.783
2021	19.583
2022	19.375