Year	Percent
1991	49.906
1992	47.534
1993	43.549
1994	40.009
1995	38.428
1996	40.054
1997	37.934
1998	37.148
1999	33.669
2000	33.546
2001	33.735
2002	31.354
2003	28.22
2004	29.812
2005	30.537
2006	28.826
2007	28.245
2008	28.713
2009	32.681
2010	31.745
2011	32.295
2012	32.351
2013	30.663
2014	29.6
2015	28.446
2016	29.259
2017	29.52
2018	29.175
2019	28.837
2020	28.5
2021	28.283
2022	27.919