Year	%
1988	76.45073
1989	77.13454
1990	78.87771
1991	80.0195
1992	81.69642
1993	81.54955
1994	82.85909
1995	85.11417
1996	85.7454
1997	85.85172
1998	86.07132
1999	86.80774
2000	87.31224
2001	88.62734
2002	89.65542
2003	88.8923
2004	88.90205
2005	89.91546
2006	90.87938
2007	91.31572
2008	91.24717
2010	91.62866
2011	91.57362
2012	90.44522
2013	90.30597
2014	90.4861
2015	90.95731
2016	90.60188
2017	91.06873