Year	Percent
1991	31.461
1992	30.32
1993	29.394
1994	28.468
1995	28.55
1996	27.41
1997	26.428
1998	25.566
1999	24.856
2000	22.988
2001	22.027
2002	21.3
2003	20.56
2004	19.289
2005	18.977
2006	17.861
2007	17.134
2008	17.136
2009	17.965
2010	17.114
2011	18.98
2012	18.555
2013	18.769
2014	18.599
2015	18.308
2016	18.095
2017	18.027
2018	18.036
2019	18.027
2020	17.997
2021	17.938
2022	17.858