Year	% of total
1971	15.49219611064557
1972	15.789057590290087
1973	13.442871614559603
1974	12.050552346584915
1975	13.448851146152629
1976	11.454187617386122
1977	13.705941383897821
1978	13.696349248374664
1979	16.09590745398939
1980	14.131919844744528
1981	13.296565854153949
1982	15.070231681232112
1983	10.736508338873964
1984	11.747747077478214
1985	10.020593385578952
1986	14.776487028136446
1987	15.155598354259151
1988	14.404939711070583
1989	14.148003569968887
1990	15.06127101738387
1991	13.327232592794116
1992	9.535052059631107
1993	6.37932764066257
1994	13.236878269722496
1995	12.539776383937234
1996	17.7979415491053
1997	12.641412959640865
1998	15.003697089460916
1999	17.208284461741165
2000	14.858608561184344
2001	12.603888311368841
2002	13.417923185822364
2003	15.83807438114507
2004	14.738290531222887
2005	13.797883845506808
2006	12.019334162865816
2007	12.789387699949287
2008	14.29407394770733
2009	24.101515133035523
2010	22.035708977706044
2011	19.909089371301487
2012	17.21810260525303
2013	17.385897447091413
2014	17.80063303121627