Year	% net
1977	18.30652
1978	18.87865
1979	19.61625
1980	20.84066
1983	22.14841
1984	22.3378
1985	22.08209
1986	21.86232
1987	21.94663
1988	22.02896
1989	21.74791
1990	21.29488
1991	22.15039
1992	22.72053
1993	23.22258
1994	23.94181
1995	24.91542
1996	25.34969
1997	25.74441
1998	26.53221
1999	27.15346
2000	28.08122
2001	28.83099
2002	29.88892
2003	31.0066
2004	31.8587
2005	32.3161
2006	33.54687
2007	34.48067
2008	35.28721
2009	36.30765
2010	37.08923
2011	37.46387
2012	38.43583
2013	38.75785
2014	39.29851
2015	40.22954
2016	40.9799
2017	40.73329
2018	42.07594