Year	%
1971	43.6655
1972	37.25169
1973	45.06294
1974	43.02437
1975	45.29155
1976	56.78258
1977	56.28113
1978	65.02335
1980	70.9865
1989	45.97823
1990	70.92946
1991	46.19124
1996	47.09526
1998	49.87769
1999	48.44147
2000	50.03469
2001	59.38882
2002	59.33287
2003	64.50274
2004	78.30493
2005	73.20934
2006	54.32512
2007	61.70592
2008	60.4181
2009	68.96427
2010	73.78217
2011	65.46206
2012	70.53683
2013	66.96961
2015	60.00972