Year	Percent
1991	69.799
1992	69.574
1993	69.176
1994	68.694
1995	68.185
1996	67.24
1997	66.295
1998	65.349
1999	64.38
2000	63.39
2001	62.998
2002	62.587
2003	62.177
2004	61.806
2005	61.497
2006	61.566
2007	61.85
2008	62.113
2009	62.35
2010	62.563
2011	62.761
2012	62.61
2013	62.358
2014	61.981
2015	61.468
2016	60.895
2017	60.921
2018	60.952
2019	60.989
2020	61.031
2021	61.075
2022	61.121