Year	%
1972	25.67365
1973	29.29628
1974	31.24768
1975	32.25113
1976	34.05561
1977	29.94965
1978	35.95258
1979	34.62399
1980	35.6218
1981	35.46952
1982	40.55025
1983	39.69214
1984	41.32813
1985	40.77407
1986	44.36359
1987	44.90472
1990	45.09321
1999	30.90724
2006	44.92243
2007	59.50987
2008	51.28681
2010	60.80533
2011	65.11651
2014	67.89956
2015	66.49127