Year	Percent
1961	29.74781
1962	29.78436
1963	29.82091
1964	29.85746
1965	29.89401
1966	29.93421
1967	29.97076
1968	30.00731
1969	30.05117
1970	30.10234
1971	30.04386
1972	30.34357
1973	30.60307
1974	30.89547
1975	31.19883
1976	31.37792
1977	31.56067
1978	31.74342
1979	31.92617
1980	32.10892
1981	32.29167
1982	32.47442
1983	32.65716
1984	32.83991
1985	33.02266
1986	33.20541
1987	33.40643
1988	34.95614
1989	35.08772
1990	34.99635
1991	34.90497
1992	34.8136
1993	34.72222
1994	34.47003
1995	34.53947
1996	34.90497
1997	36.00146
1998	36.44006
1999	36.79094
2000	37.14547
2001	37.51096
2002	37.86915
2003	38.22368
2004	38.6367
2005	39.04605
2006	39.43713
2007	39.80629
2008	40.20285
2009	40.61404
2010	41.08918
2011	41.71418
2012	42.17471
2013	42.85453
2014	43.3114
2015	43.80848
2016	44.23246
2017	44.65278
2018	45.36915
2019	45.75658
2020	46.1038
2021	46.56433