Year	% of total primary
1971	33.1699409484863
1974	34.4270896911621
1978	23.5884399414062
1981	20.7420692443848
1982	19.6123905181885
1983	19.149959564209
1984	18.1267604827881
1985	17.47705078125
1986	17.3127708435059
1987	17.6173706054688
1988	17.3527507781982
1989	17.4210891723633
1990	17.4832401275635
1991	17.57373046875
1992	17.0694007873535
1993	17.0950202941895
1994	17.7674694061279
1995	17.6953105926514
1996	17.6519203186035
1997	17.3030300140381
1998	17.9849796295166
1999	17.9017601013184
2000	15.7197504043579
2001	15.8649196624756
2002	15.9707498550415
2003	16.142650604248
2004	16.3223304748535
2005	16.647180557251
2006	15.8986501693726
2007	18.196159362793
2008	16.1096801757812
2009	16.3789405822754
2010	16.8166999816895
2011	17.1333999633789
2012	17.3307495117188
2013	17.944709777832
2014	18.4064197540283
2015	20.2072601318359
2017	21.8670692443848
2018	22.8545207977295