Year	Percent
1991	37.412
1992	37.526
1993	38.044
1994	37.564
1995	37.409
1996	37.442
1997	37.863
1998	39.165
1999	39.037
2000	38.881
2001	39.091
2002	38.795
2003	38.537
2004	37.995
2005	37.642
2006	36.862
2007	36.098
2008	35.63
2009	34.796
2010	34.404
2011	34.167
2012	34.441
2013	33.739
2014	33.239
2015	32.582
2016	32.666
2017	32.589
2018	32.568
2019	32.546
2020	32.525
2021	32.505
2022	32.484