Year	Percent
1961	13.24687
1962	13.35859
1963	13.61719
1964	13.80312
1965	13.86719
1966	13.80859
1967	13.81563
1968	13.89062
1969	13.92109
1970	13.99453
1971	14.00156
1972	14.50391
1973	14.54314
1974	14.58472
1975	14.6263
1976	14.66788
1977	14.72509
1978	14.77448
1979	14.82387
1980	14.86545
1981	14.90703
1982	14.95643
1983	14.99801
1984	15.0474
1985	15.09679
1986	15.154
1987	15.20339
1988	15.25278
1989	15.30218
1990	17.52891
1991	17.57831
1992	17.6277
1993	17.67709
1994	17.46078
1995	17.57562
1996	17.69039
1997	17.80516
1998	17.91992
1999	18.03469
2000	18.14945
2001	18.26422
2002	18.37898
2003	18.49375
2004	18.60852
2005	18.74438
2006	18.8693
2007	18.99422
2008	19.11992
2009	19.24484
2010	19.37055
2011	19.50328
2012	19.60958
2013	19.50576
2014	19.39967
2015	19.2936
2016	19.09609
2017	19.15477
2018	19.29577
2019	19.12366
2020	19.5289
2021	19.93413