Year	Percent
1990	36.4
1991	34.155
1992	31.979
1993	29.879
1994	27.86
1995	27.726
1996	27.588
1997	27.543
1998	27.373
1999	27.099
2000	26.974
2001	26.934
2002	26.9
2003	27.062
2004	27.122
2005	27.06
2006	27.036
2007	27.058
2008	27.259
2009	27.549
2010	27.557
2011	27.606
2012	27.533
2013	27.603
2014	27.695
2015	27.839
2016	27.894
2017	27.945
2018	27.996
2019	28.048
2020	28.099
2021	28.15
2022	28.201
2023	28.252
2024	28.303
2025	28.354
2026	28.406
2027	28.457
2028	28.508
2029	28.559
2030	28.61