Year	% of internal resources
1970	18.867537313432834
1971	20.14328358208955
1972	21.41902985074627
1973	22.694776119402984
1974	23.9705223880597
1975	25.24626865671642
1976	25.8429104477612
1977	26.43955223880597
1978	27.036194029850748
1979	27.63283582089552
1980	28.229477611940297
1981	28.70783582089552
1982	29.18619402985075
1983	29.664552238805967
1984	30.142910447761196
1985	30.621268656716417
1986	30.15634328358209
1987	29.69141791044776
1988	29.22649253731343
1989	28.7615671641791
1990	28.296641791044774
1991	26.629664179104477
1992	24.96268656716418
1993	24.74365671641791
1994	24.524626865671642
1995	24.30559701492537
1996	24.0865671641791
1997	23.867537313432834
1998	23.46679104477612
1999	23.066044776119405
2000	22.665298507462687
2001	22.26455223880597
2002	21.86380597014925
2003	21.976119402985073
2004	22.08619402985075
2005	22.197388059701492
2006	22.308582089552235
2007	22.425373134328357
2008	21.19402985074627
2009	21.473880597014926
2010	20.279850746268654
2011	22.220149253731343
2012	21.399253731343286
2013	20.970149253731343
2014	19.833955223880597
2015	19.492537313432837
2016	19.19589552238806
2017	18.80597014925373
2018	17.90671641791045
2019	16.76115485074627
2020	16.169776119402986