Year	Percent
1990	20.207
1991	20.165
1992	20.183
1993	20.156
1994	20.065
1995	20.006
1996	19.918
1997	19.848
1998	19.751
1999	19.649
2000	19.583
2001	19.491
2002	19.39
2003	19.285
2004	19.18
2005	19.086
2006	19.012
2007	18.93
2008	18.85
2009	18.781
2010	18.715
2011	18.669
2012	18.624
2013	18.58
2014	18.526
2015	18.462
2016	18.415
2017	18.351
2018	18.288
2019	18.224
2020	18.161
2021	18.097
2022	18.033
2023	17.97
2024	17.906
2025	17.842
2026	17.779
2027	17.715
2028	17.651
2029	17.588
2030	17.524