Year	Percent
1961	21.90545
1962	21.57371
1963	21.77068
1964	22.71408
1965	23.61601
1966	23.99959
1967	24.21729
1968	24.28986
1969	24.22766
1970	24.09289
1971	23.83371
1972	23.53307
1973	23.54344
1974	23.51234
1975	23.5538
1976	23.53307
1977	23.50197
1978	23.4605
1979	23.34646
1980	23.29463
1981	23.2739
1982	23.25316
1983	23.18059
1984	23.10802
1985	23.01472
1986	22.98362
1987	23.00435
1988	22.95252
1989	22.77628
1990	22.58967
1991	22.40307
1992	22.14389
1993	21.95729
1994	21.72921
1995	21.2316
1996	20.81692
1997	20.55774
1998	20.41261
1999	20.2571
2000	20.45407
2001	20.10544
2002	19.82643
2003	19.64876
2004	19.55175
2005	19.42179
2006	19.17836
2007	18.98473
2008	18.73389
2009	18.49372
2010	18.24074
2011	18.06873
2012	18.37427
2013	18.15429
2014	17.94417
2015	17.81518
2016	17.44607
2017	17.19516
2018	16.94011
2019	16.77254
2020	16.60861
2021	16.42418