Year	Percent
1991	55.706
1992	55.813
1993	56.176
1994	56.865
1995	57.171
1996	57.47
1997	58.216
1998	58.96
1999	59.528
2000	60.478
2001	61.06
2002	61.466
2003	62.021
2004	62.541
2005	62.808
2006	63.294
2007	63.599
2008	63.437
2009	62.71
2010	62.86
2011	63.069
2012	63.04
2013	63.314
2014	63.77
2015	64.127
2016	64.431
2017	64.564
2018	64.786
2019	65.08
2020	65.449
2021	65.861
2022	66.27