Year	%
1977	56.5361
1978	56.61452
1979	56.7945
1980	56.85411
1981	53.7953
1982	54.25428
1983	54.73525
1984	54.27277
1985	56.69805
1986	57.42096
1987	58.82654
1988	59.11497
1989	58.87713
1990	59.62674
1991	59.97701
1992	61.082
1993	61.11308
1994	62.75241
1995	64.21509
1996	66.13329
1997	67.02063
1998	69.77292
1999	69.96997
2000	71.57375
2001	73.9096
2002	74.70292
2003	76.45542
2004	79.03192
2005	79.53073
2006	80.729
2007	81.57588
2008	79.01662
2009	80.01064
2010	80.54254
2011	80.98914
2012	80.72253
2013	80.8348
2014	80.25501
2015	81.09692
2016	80.11996
2017	79.97081