Year	% of total
1971	22.925838130714528
1972	23.188176716984117
1973	24.541465061325532
1974	23.30232558139535
1975	24.881573117949767
1976	25.66851998940958
1977	24.798691882886494
1978	19.89890530597595
1979	19.70192077787519
1980	22.02186067596837
1981	22.425912098663716
1982	25.65812565812566
1983	24.421551984745253
1984	24.56522706044567
1985	27.4472550535734
1986	27.07793400404057
1987	24.08001691039413
1988	40.334188263216326
1989	48.14594840727762
1990	39.164367363027196
1991	39.1641646308487
1992	37.255954617848644
1993	35.6941015980252
1994	33.92810082626691
1995	39.553831231813774
1996	46.51005940935051
1997	44.154748402445435
1998	45.949305518024104
1999	56.496451961673735
2000	54.6473962433922
2001	47.71125783720801
2002	47.684510911394504
2003	51.710311854829946
2004	54.801577397294466
2005	52.446180242864315
2006	46.29031805294333
2007	51.04687427268072
2008	54.21861122989375
2009	51.22991494352808
2010	49.98203779248461
2011	44.818802825055
2012	48.31412624329964
2013	47.23536432793109
2014	48.19967859159416
2015	49.48226025648986