Year	Percent
1990	81.38
1991	81.55
1992	81.76
1993	81.478
1994	82.038
1995	81.953
1996	81.765
1997	81.694
1998	81.842
1999	81.708
2000	81.599
2001	81.574
2002	81.56
2003	81.396
2004	81.211
2005	81
2006	79.773
2007	78.488
2008	77.144
2009	75.743
2010	74.284
2011	72.77
2012	71.2
2013	70.921
2014	70.64
2015	70.437
2016	70.253
2017	69.982
2018	69.711
2019	69.44
2020	69.169
2021	68.898
2022	68.627
2023	68.356
2024	68.085
2025	67.814
2026	67.543
2027	67.273
2028	67.002
2029	66.731
2030	66.46