Year	Percent
1990	68.091
1991	68.129
1992	68.125
1993	68.152
1994	68.183
1995	68.214
1996	68.241
1997	68.276
1998	68.311
1999	68.293
2000	68.3
2001	67.318
2002	66.32
2003	65.308
2004	64.282
2005	63.242
2006	62.19
2007	66.72
2008	68.04
2009	65.36
2010	63.913
2011	62.44
2012	60.7
2013	62.86
2014	61.4
2015	59.84
2016	59.866
2017	59.66
2018	59.453
2019	59.246
2020	59.039
2021	58.833
2022	58.626
2023	58.419
2024	58.213
2025	58.006
2026	57.799
2027	57.592
2028	57.386
2029	57.179
2030	56.972