Year	Percent
1990	77.58
1991	77.497
1992	77.364
1993	77.289
1994	77.232
1995	77.063
1996	77.112
1997	77.119
1998	77.056
1999	76.954
2000	76.817
2001	76.739
2002	76.631
2003	76.521
2004	76.485
2005	76.528
2006	76.718
2007	76.951
2008	77.141
2009	77.39
2010	77.603
2011	77.858
2012	78.08
2013	78.241
2014	78.36
2015	78.42
2016	78.444
2017	78.435
2018	78.399
2019	78.354
2020	78.313
2021	78.284
2022	78.257
2023	78.238
2024	78.233
2025	78.247
2026	78.285
2027	78.342
2028	78.411
2029	78.482
2030	78.549