Year	Percent
1990	67.113
1991	66.32
1992	66.397
1993	65.993
1994	66.573
1995	66.752
1996	66.755
1997	66.238
1998	66.451
1999	66.199
2000	66.19
2001	65.137
2002	65.048
2003	65.124
2004	65.367
2005	64.906
2006	65.061
2007	64.933
2008	64.909
2009	64.765
2010	64.47
2011	63.475
2012	62.735
2013	62.349
2014	61.483
2015	61.053
2016	60.965
2017	60.584
2018	60.186
2019	59.75
2020	59.266
2021	58.691
2022	58.082
2023	57.458
2024	56.841
2025	56.244
2026	55.627
2027	55.038
2028	54.467
2029	53.901
2030	53.331