Year	Percent
1991	32.446
1992	32.646
1993	33.635
1994	32.969
1995	32.711
1996	32.494
1997	31.915
1998	30.782
1999	30.383
2000	30.472
2001	30.039
2002	29.637
2003	30.686
2004	30.128
2005	29.952
2006	29.81
2007	29.229
2008	28.811
2009	28.253
2010	27.772
2011	27.086
2012	26.18
2013	25.088
2014	23.852
2015	22.597
2016	22.014
2017	21.632
2018	21.073
2019	20.56
2020	20.081
2021	19.587
2022	19.112