Year	Percent
1991	37.261
1992	36.928
1993	37.039
1994	37.108
1995	37.664
1996	37.631
1997	37.58
1998	37.508
1999	37.068
2000	36.627
2001	36.152
2002	35.686
2003	35.206
2004	34.708
2005	34.221
2006	33.754
2007	33.287
2008	32.818
2009	32.351
2010	31.899
2011	31.476
2012	30.997
2013	30.577
2014	30.174
2015	29.792
2016	29.423
2017	29.293
2018	29.165
2019	29.028
2020	28.973
2021	28.901
2022	28.813