Year	Percent
1990	55.715
1991	56.072
1992	56.238
1993	55.983
1994	56.425
1995	55.901
1996	55.284
1997	55.339
1998	55.202
1999	55.045
2000	54.345
2001	53.607
2002	53.148
2003	52.664
2004	52.165
2005	51.723
2006	51.545
2007	50.835
2008	50.774
2009	51.464
2010	51.479
2011	50.866
2012	50.914
2013	51.252
2014	51.186
2015	51.045
2016	50.302
2017	50.195
2018	50.082
2019	49.977
2020	49.887
2021	49.814
2022	49.755
2023	49.708
2024	49.665
2025	49.621
2026	49.582
2027	49.545
2028	49.51
2029	49.474
2030	49.435