Year	%
1978	62.91003
1979	62.80154
1980	62.57041
1981	59.93943
1982	60.8353
1983	59.50617
1984	59.18637
1985	61.03929
1986	62.09784
1987	62.87969
1988	63.53884
1989	63.56676
1990	63.42099
1991	63.90441
1992	63.61484
1993	63.52883
1994	64.28993
1998	67.7957
1999	67.84342
2000	69.07942
2001	71.26869
2002	73.12104
2003	74.64521
2004	75.96657
2005	76.7081
2006	78.4151
2007	78.97071
2008	78.21384
2009	78.96504
2010	79.07511
2011	80.16708
2012	78.82504
2013	79.65494
2014	79.14676
2015	80.51983