Year	Percent
1990	84.5
1991	84.408
1992	84.335
1993	84.276
1994	84.226
1995	83.977
1996	83.69
1997	83.398
1998	83.107
1999	82.828
2000	82.566
2001	82.647
2002	82.743
2003	82.852
2004	82.969
2005	83.091
2006	82.57
2007	82.057
2008	81.548
2009	81.041
2010	80.533
2011	80.04
2012	79.544
2013	79.408
2014	79.258
2015	79.091
2016	78.884
2017	78.837
2018	78.792
2019	78.751
2020	78.717
2021	78.676
2022	78.643
2023	78.622
2024	78.618
2025	78.634
2026	78.656
2027	78.702
2028	78.758
2029	78.804
2030	78.826