Year	Percent
1991	74.9
1992	75.019
1993	74.909
1994	74.365
1995	73.694
1996	73.295
1997	72.822
1998	72.17
1999	71.555
2000	71.101
2001	71.188
2002	71.388
2003	71.649
2004	72.68
2005	73.43
2006	74.797
2007	75.083
2008	74.876
2009	74.679
2010	74.422
2011	74.211
2012	74.114
2013	74.227
2014	74.038
2015	73.732
2016	73.583
2017	73.537
2018	73.496
2019	73.449
2020	73.409
2021	73.446
2022	73.485