Year	% of total teachers
1997	85.7020416259766
1998	84.586799621582
1999	85.3730697631836
2000	84.8107070922852
2001	84.6953506469727
2002	84.7035217285156
2003	84.3294830322266
2004	84.4419631958008
2005	83.4007034301758
2006	83.8620223999023
2007	83.3143997192383
2008	81.8242874145508
2009	80.4979934692383
2010	81.1584701538086
2011	80.590202331543
2012	78.5889434814453
2013	81.4285278320312
2014	82.3828277587891
2015	82.1277694702148
2016	80.8205718994141
2017	80.5207138061523
2018	82.4013977050781
2019	80.7848205566406
2020	79.7922821044922