Year	Percent
1990	81.76
1991	81.727
1992	81.345
1993	81.048
1994	80.841
1995	80.688
1996	80.403
1997	80.201
1998	80.074
1999	79.992
2000	79.914
2001	79.063
2002	78.585
2003	78.28
2004	78.127
2005	78.044
2006	77.474
2007	76.986
2008	76.658
2009	76.502
2010	76.448
2011	76.36
2012	76.177
2013	75.926
2014	75.659
2015	75.258
2016	74.858
2017	74.683
2018	74.495
2019	74.3
2020	74.1
2021	73.899
2022	73.707
2023	73.497
2024	73.245
2025	72.93
2026	72.574
2027	72.166
2028	71.721
2029	71.27
2030	70.829