Year	% of total primary
1970	26.1050090789795
1971	25.1145095825195
1972	24.4943199157715
1973	23.5863800048828
1974	22.5810604095459
1975	22.7872104644775
1976	24.2862701416016
1980	28.505880355835
1981	29.769229888916
1982	30.0233592987061
1983	31.4637908935547
1984	31.2396392822266
1986	28.7889003753662
1987	28.1408500671387
1988	23.4624900817871
1989	24.2837791442871
1991	25.3615207672119
1992	26.3938503265381
1993	28.6429691314697
1994	29.7752494812012
1995	31.7514991760254
1996	33.1847305297852
1997	34.474048614502
1998	35.5374794006348
1999	36.0093383789062
2000	35.0994987487793
2001	33.7671699523926
2002	34.8090515136719
2003	35.8786392211914
2004	35.9428215026855
2005	35.7189407348633
2006	36.3819808959961
2007	36.5026512145996
2008	37.2919692993164
2009	36.7068786621094
2010	36.4107208251953
2011	36.612060546875
2012	37.2699012756348
2013	38.2157287597656
2014	39.2326812744141
2015	39.4088706970215
2016	40.3671798706055
2017	40.5528907775879
2018	41.1886901855469
2019	41.3395881652832
2020	41.1889305114746