Year	%
1971	58.65305
1972	57.29471
1973	56.15881
1974	56.61963
1975	56.22332
1976	56.91586
1977	56.66294
1978	57.42017
1979	57.63571
1980	57.64523
1981	51.44391
1982	53.92517
1983	54.00207
1984	53.47321
1985	56.19625
1986	56.83361
1987	58.53466
1988	59.64092
1989	59.462
1990	59.29245
1991	59.19774
1992	59.58329
1993	59.06287
1994	60.36759
1995	61.49029
1996	63.18057
1997	62.93108
1998	66.52067
1999	65.97924
2000	67.00561
2001	67.14036
2002	67.91059
2003	70.60038
2004	73.73301
2005	74.38158
2006	77.25995
2007	79.00535
2008	76.2605
2009	77.32901
2010	78.0078
2011	78.8322
2012	78.23668
2013	78.35603
2014	78.25148
2015	78.89122
2016	77.56584
2017	76.8224