Year	Percent
1991	37.722
1992	36.944
1993	35.845
1994	35.511
1995	37.127
1996	35.256
1997	34.371
1998	34.805
1999	34.253
2000	34.938
2001	34.144
2002	33.078
2003	31.664
2004	31.374
2005	31.988
2006	32.173
2007	32.293
2008	32.613
2009	31.858
2010	32.289
2011	32.272
2012	31.206
2013	31.328
2014	30.545
2015	29.99
2016	29.907
2017	29.991
2018	29.834
2019	29.676
2020	29.516
2021	29.368
2022	29.212