Year	Percent
1991	36.717
1992	36.044
1993	35.844
1994	35.69
1995	34.739
1996	34.003
1997	33.129
1998	31.161
1999	30.447
2000	30.18
2001	30.255
2002	29.343
2003	29.896
2004	30.88
2005	31.077
2006	31.252
2007	30.77
2008	30.102
2009	27.315
2010	30.236
2011	25.318
2012	30.052
2013	31.406
2014	30.814
2015	30.732
2016	30.524
2017	30.258
2018	29.988
2019	29.721
2020	29.455
2021	29.188
2022	28.928