Year	% net
1971	80.70289
1972	85.34965
1973	86.66789
1974	85.83138
1976	88.73072
1977	90.29278
1978	94.33573
1979	95.85604
1980	96.03279
1981	94.89939
1982	95.50819
1983	93.79216
1984	93.73757
1985	91.64042
1986	92.50014
1987	89.30112
1988	88.22938
1989	87.43423
1990	85.70748
1991	81.15871
1992	78.30968
1993	77.18153
1994	81.71496
1998	93.43029
1999	93.72663
2000	96.05048
2001	91.89571
2002	92.51716
2003	96.02781
2004	91.13612
2005	94.99625
2006	88.84162
2007	92.81665
2009	91.41677
2010	90.21337
2011	93.40615
2012	92.23312
2013	88.63244
2014	89.28562
2015	91.73736
2016	93.02649
2017	93.54716
2018	94.09431