Year	Percent
1991	73.895
1992	75.343
1993	75.169
1994	76.124
1995	73.756
1996	74.214
1997	73.472
1998	73.608
1999	72.76
2000	72.21
2001	72.801
2002	71.775
2003	70.87
2004	70.948
2005	71.148
2006	70.227
2007	68.138
2008	68.274
2009	68.442
2010	68.953
2011	68.255
2012	69.169
2013	68.294
2014	67.657
2015	67.765
2016	67.257
2017	66.876
2018	66.832
2019	66.782
2020	66.726
2021	66.673
2022	66.619