Year	%
1971	56.26909
1978	92.69874
1979	81.27504
1980	76.90664
1981	64.10311
1982	60.28116
1983	49.96714
1984	50.82283
1985	67.26542
1986	65.63369
1987	76.2323
1988	62.44097
1989	78.62492
1990	71.46838
1991	66.5057
1994	81.85041
1995	69.91989
1999	79.18047
2000	81.93582
2002	77.12861
2003	78.88684
2004	79.81583
2005	79.60653
2007	78.11162
2009	84.60005
2010	91.13909
2012	84.29279
2013	80.04843
2014	85.3212
2016	83.24571
2017	81.99249