Year	% net
1977	14.98175
1978	15.36249
1979	15.8974
1980	16.75024
1983	18.12253
1984	18.39569
1985	18.34159
1986	18.31204
1987	18.50724
1988	18.69466
1989	18.58864
1990	18.2695
1991	19.06751
1992	19.6725
1993	20.20399
1994	20.89601
1995	21.95332
1996	22.57271
1997	23.19076
1998	24.20341
1999	25.02192
2000	26.10125
2001	26.92863
2002	27.91417
2003	29.03142
2004	29.4728
2005	30.08863
2006	31.18289
2007	32.14792
2008	32.96999
2009	34.1441
2010	35.22685
2011	35.85177
2012	36.91835
2013	37.18216
2014	37.89062
2015	39.03294
2016	39.67625
2017	39.71058
2018	39.94525