Year	Percent
1960	12.99445
1961	12.4031
1962	13.94301
1963	13.00589
1964	14.93825
1965	13.22018
1966	12.93238
1967	12.88373
1968	12.29767
1969	11.95486
1970	12.97704
1971	12.66127
1972	12.82576
1973	14.15502
1974	13.152
1975	14.2815
1976	13.52313
1977	14.0229
1978	13.62817
1979	14.31198
1980	16.43947
1981	14.91207
1982	13.54104
1983	13.59473
1984	13.58022
1985	15.25999
1986	15.01374
1987	15.49431
1988	15.98415
1989	15.14587
1990	15.14356
1991	16.05904
1992	16.6914
1993	17.57366
1994	18.00589
1995	17.91688
1996	18.93919
1997	19.17481
1998	19.59558
1999	18.35396
2000	19.44348
2001	22.23518
2002	20.78314
2003	19.103
2004	17.21976
2005	18.2853
2006	19.90813
2007	20.23057
2008	20.1887
2009	23.03851
2010	19.84252
2011	21.47284
2012	21.51897
2013	19.98772
2014	21.07577
2015	20.01296
2016	19.25303
2017	21.27035