Year	%
1972	68.73623
1973	67.16426
1974	66.69734
1975	66.50029
1976	69.49078
1977	68.40603
1978	68.46762
1979	69.39186
1980	69.79485
1981	69.93494
1982	71.29935
1983	73.57971
1984	72.31283
1985	71.10746
1986	73.50899
1987	74.01442
1988	75.70168
1989	76.74221
1990	79.85149
1991	78.85885
1992	80.0352
1993	80.05516
1994	81.364
1995	81.84956
1996	81.63108
1997	83.26721
1998	83.93367
1999	83.42341
2000	84.47295
2001	84.78756
2002	86.49412
2003	87.47256
2004	88.45057
2005	89.26696
2006	88.13025
2007	88.65654
2008	88.58982
2009	89.3495
2010	89.85963
2011	90.24725
2012	89.85933
2013	91.01365
2014	90.45282
2015	90.52875
2016	90.17411
2017	90.07839