Year	Percent
1991	31.642
1992	33.589
1993	31.241
1994	18.878
1995	31.895
1996	29.057
1997	31.732
1998	29.346
1999	29.749
2000	31.832
2001	31.796
2002	31.677
2003	29.866
2004	31.082
2005	31.137
2006	29.817
2007	27.238
2008	28.44
2009	25.147
2010	29.698
2011	29.521
2012	27.029
2013	30.248
2014	29.152
2015	28.333
2016	29.581
2017	29.546
2018	29.509
2019	29.565
2020	29.594
2021	29.643
2022	29.665