Year	Percent
1961	42.34973
1962	42.4153
1963	42.48087
1964	42.54645
1965	42.61202
1966	42.6776
1967	42.74317
1968	42.76503
1969	42.87432
1970	42.93989
1971	43.00546
1972	43.07104
1973	43.12568
1974	43.18033
1975	43.23497
1976	43.28962
1977	43.34426
1978	43.39891
1979	43.45355
1980	43.48634
1981	43.51913
1982	43.55191
1983	43.5847
1984	43.61749
1985	43.65027
1986	43.68306
1987	43.72678
1988	43.77049
1989	43.77049
1990	43.31148
1991	42.84153
1992	42.38251
1993	43.26776
1994	43.19126
1995	42.88525
1996	40.76503
1997	39.14754
1998	40.68306
1999	42.21858
2000	43.23913
2001	42.11825
2002	42.37945
2003	41.67956
2004	42.29082
2005	41.80485
2006	41.08079
2007	40.02318
2008	40.73314
2009	40.34916
2010	39.89704
2011	39.84452
2012	40.00884
2013	40.40273
2014	39.99624
2015	39.72224
2016	39.50665
2017	40.10009
2018	40.7919
2019	43.12532
2020	43.16609
2021	43.25386