Year	Percent
1991	34.996
1992	36.973
1993	40.034
1994	43.898
1995	44.573
1996	44.586
1997	42.492
1998	40.581
1999	41.174
2000	40.071
2001	38.948
2002	37.12
2003	34.858
2004	35.21
2005	36.535
2006	35.856
2007	34.922
2008	38.413
2009	32.329
2010	32.272
2011	32.189
2012	31.748
2013	31.061
2014	31.199
2015	30.972
2016	30.938
2017	31.787
2018	31.696
2019	31.432
2020	31.007
2021	30.614
2022	30.106