Year	Percent
1991	37.132
1992	35.674
1993	31.876
1994	36.884
1995	37.453
1996	37.728
1997	42.057
1998	37.892
1999	35.024
2000	34.775
2001	33.974
2002	34.082
2003	32.603
2004	37.929
2005	38.066
2006	38.944
2007	43.009
2008	42.177
2009	38.35
2010	36.877
2011	35.026
2012	29.692
2013	29.09
2014	29.287
2015	32.148
2016	31.205
2017	32.967
2018	32.72
2019	32.349
2020	31.837
2021	31.232
2022	30.543