Year	% of total primary
1971	28.141040802002
1972	26.6535892486572
1973	26.9746704101562
1974	24.9854907989502
1981	15.5813798904419
1982	13.6148195266724
1983	12.5448303222656
1984	12.3050804138184
1985	11.5746202468872
1986	11.0468196868896
1987	10.5049600601196
1988	10.3432197570801
1989	10.7183704376221
1990	11.4666595458984
1991	12.532600402832
1992	13.6398601531982
1993	11.6923198699951
1994	10.6200304031372
1995	9.10039043426514
1996	7.58806991577148
1997	6.68856000900269
1998	6.23410987854004
2003	5.28216981887817
2008	5.4201397895813
2009	6.00548982620239
2010	6.00525999069214
2011	5.3553900718689
2012	4.00205993652344
2014	4.15647983551025
2015	4.95432996749878
2020	4.23686981201172
2021	4.4282398223877