Year	%
1972	45.21813
1973	42.02048
1975	39.72803
1976	39.73296
1977	45.29779
1978	44.95398
1979	52.93695
1980	50.52067
1982	41.83371
1983	40.16159
1984	42.54663
1985	42.90726
1986	42.59271
1987	42.54918
1993	62.87894
1995	59.82874
1996	61.08926
1997	57.29041
1999	49.43688
2000	62.56459
2006	69.01947
2008	66.89039
2011	68.4251
2013	84.84545
2014	90.45018
2015	89.33549
2016	92.50092