Year	Percent
1990	73.86
1991	73.1
1992	72.325
1993	71.537
1994	70.736
1995	69.922
1996	69.095
1997	68.255
1998	67.403
1999	66.737
2000	66.064
2001	65.384
2002	64.697
2003	64.005
2004	63.307
2005	62.603
2006	61.894
2007	61.179
2008	60.46
2009	59.736
2010	59.008
2011	58.277
2012	57.541
2013	56.802
2014	56.06
2015	56.064
2016	56.079
2017	55.798
2018	55.517
2019	55.236
2020	54.955
2021	54.673
2022	54.392
2023	54.111
2024	53.83
2025	53.549
2026	53.268
2027	52.987
2028	52.705
2029	52.424
2030	52.143