Year	Percent
1991	34.975
1992	35.521
1993	35.659
1994	34.627
1995	33.393
1996	32.954
1997	31.914
1998	32.224
1999	33.206
2000	33.314
2001	32.822
2002	31.511
2003	31.223
2004	30.45
2005	30.275
2006	29.342
2007	29.031
2008	29.005
2009	28.25
2010	28.751
2011	28.813
2012	29.536
2013	30.388
2014	29.609
2015	29.013
2016	28.743
2017	28.547
2018	28.474
2019	28.449
2020	28.409
2021	28.384
2022	28.386