Year	Percent
1961	26.6333
1962	26.72267
1963	26.76736
1964	26.81205
1965	26.85673
1966	26.94611
1967	27.03548
1968	27.08017
1969	27.08017
1970	27.16954
1971	27.21423
1972	27.52704
1973	27.61641
1974	27.67003
1975	28.01859
1976	28.3314
1977	29.0017
1978	29.10895
1979	29.10895
1980	29.10895
1981	29.17151
1982	29.21619
1983	29.22513
1984	29.28769
1985	29.29663
1986	29.35919
1987	29.35919
1988	29.35919
1989	30.1278
1990	29.672
1991	29.86862
1992	29.98481
1993	31.70971
1994	31.45947
1995	31.10198
1996	31.10198
1997	30.3423
1998	30.3423
1999	29.82393
2000	26.23112
2001	26.24006
2002	27.06229
2003	28.17946
2004	28.06328
2005	28.15265
2006	28.24202
2007	28.24202
2008	28.45652
2009	28.58164
2010	29.20726
2011	29.59156
2012	30.01162
2013	30.11887
2014	30.16355
2015	30.16355
2016	30.60148
2017	31.17347
2018	31.36116
2019	31.36116
2020	31.62034
2021	31.95996