Year	% of total primary
1970	25.3581295013428
1971	25.4693698883057
1972	25.1199398040771
1973	24.663990020752
1974	23.8737697601318
1975	23.1940002441406
1976	22.3419704437256
1977	21.7546901702881
1978	21.2580890655518
1979	20.6043300628662
1980	20.1987590789795
1981	20.0087699890137
1982	19.6692600250244
1983	19.4213695526123
1984	19.2754096984863
1985	19.2688102722168
1986	19.1489391326904
1987	19.0781497955322
1988	19.0536708831787
1989	19.2578601837158
1990	19.6697597503662
1991	19.6754703521729
1992	20.0279502868652
1993	20.4447898864746
1994	20.525899887085
1995	20.381420135498
1996	20.3238391876221
1997	20.4067897796631
1998	16.2237796783447
1999	15.4538803100586
2000	15.5796298980713
2001	16.0387992858887
2002	16.098840713501
2003	16.2784805297852
2004	16.7343196868896
2005	17.2079906463623
2006	17.5305690765381
2007	18.4240398406982
2008	19.3031997680664
2009	19.5084095001221
2010	19.1265697479248
2011	19.0799007415771
2012	18.8946495056152
2013	18.5332107543945
2014	18.3141002655029
2015	18.2410507202148
2016	18.357780456543
2017	19.1187591552734
2018	19.2245101928711
2019	19.8479099273682
2020	20.0849895477295
2021	20.1658096313477
2022	20.3510894775391