Year	Percent
1991	39.073
1992	38.954
1993	38.987
1994	38.614
1995	38.227
1996	37.842
1997	37.578
1998	37.431
1999	37.315
2000	31.901
2001	31.865
2002	31.778
2003	31.63
2004	31.39
2005	31.135
2006	31.196
2007	30.766
2008	30.817
2009	30.998
2010	30.378
2011	30.01
2012	29.846
2013	29.63
2014	29.538
2015	29.569
2016	29.583
2017	29.68
2018	29.672
2019	29.654
2020	29.634
2021	29.611
2022	29.588