Year	%
1971	38.22986
1972	41.84912
1973	37.8345
1977	36.1054
1980	52.02686
1981	69.30752
1982	72.98445
1985	53.97162
1986	44.79909
1987	56.41205
1988	56.07521
1989	49.6894
1990	54.5548
2004	73.74336
2008	62.82517
2011	80.54362