Year	% net
1971	72.8804
1973	81.93558
1974	83.57957
1975	83.73304
1976	84.46257
1977	85.35489
1978	85.05841
1979	84.88067
1980	85.78521
1981	85.79782
1982	86.06373
1983	86.49661
1984	88.33161
1985	89.81324
1986	91.45233
1987	94.83507
1988	94.70753
1989	95.03837
1990	94.73268
1991	95.76462
1992	96.16329
1993	96.20813
1994	96.43579
1995	96.46908
1996	96.37966
1997	95.58284
1998	94.04512
1999	93.53928
2000	93.86005
2001	94.56479
2002	94.88283
2003	91.70143
2004	92.51197
2005	92.57075
2006	89.91412
2007	91.00896
2008	91.75748
2009	92.80847
2010	92.96128
2013	67.96461