Year	% of total primary
1971	23.9680595397949
1972	22.4314594268799
1973	21.5834808349609
1974	19.7152194976807
1975	17.9581108093262
1976	17.5102806091309
1981	16.0212898254395
1982	16.4034805297852
1983	19.6494102478027
1984	22.9878807067871
1985	25.8914794921875
1986	28.2751808166504
1987	30.7509994506836
1988	33.9607009887695
1989	36.3110885620117
1990	37.340160369873
1991	24.9783992767334
1992	28.0719795227051
1993	30.0219593048096
1994	32.4417495727539
1995	31.0892601013184
1996	33.1977386474609
1997	32.8790016174316
1999	32.2476005554199
2000	31.0988597869873
2001	30.6359100341797
2002	30.4037303924561
2003	30.9880790710449
2004	32.3407287597656
2005	33.0297889709473
2006	34.4636497497559
2007	36.89501953125
2008	37.6303901672363
2009	38.4354286193848
2010	39.1839408874512
2011	41.0375213623047
2012	40.9944381713867
2013	41.7308006286621
2015	42.5697898864746
2016	41.7763595581055
2017	42.1484489440918
2018	41.8483581542969
2019	40.3307113647461
2020	40.8954010009766
2021	38.4232406616211