Year	Percent
1990	69.375
1991	69.207
1992	68.426
1993	67.636
1994	66.84
1995	66.044
1996	65.313
1997	64.631
1998	63.994
1999	63.401
2000	62.853
2001	62.244
2002	60.709
2003	60.841
2004	61.823
2005	61.117
2006	59.954
2007	61.637
2008	61.414
2009	60.353
2010	59.825
2011	59.878
2012	58.964
2013	57.764
2014	58.931
2015	59.379
2016	58.007
2017	57.692
2018	57.39
2019	57.074
2020	56.727
2021	56.319
2022	55.893
2023	55.46
2024	55.045
2025	54.661
2026	54.269
2027	53.915
2028	53.597
2029	53.308
2030	53.044