Year	% of total
1971	14.911015226255092
1972	15.457960808340967
1973	15.421562226338182
1974	16.568899014724447
1975	15.981919979725292
1976	15.843921601367974
1977	15.967631961695725
1978	15.171626219295373
1979	15.633373073188967
1980	16.261952482254934
1981	16.673673478779328
1982	17.10228773159476
1983	17.38428340787214
1984	17.318315230144655
1985	17.324414643303378
1986	16.823168368065538
1987	16.356709797126285
1988	16.510505193867154
1989	16.356203831816984
1990	24.168083501083373
1991	24.533211602429667
1992	24.8050661016956
1993	25.932979441181246
1994	26.961956715343593
1995	27.255726966699616
1996	26.001797403079056
1997	26.02365230824783
1998	26.412704717966122
1999	25.526479597175573
2000	25.106409758896213
2001	24.994010884283917
2002	24.186353319956115
2003	22.363408946613774
2004	22.958018473797758
2005	22.57695333186173
2006	21.595655030914774
2007	21.070714728638713
2008	21.596469280954228
2009	21.822267738277407
2010	21.39902101148515
2011	19.849424302080948
2012	21.01267431995434
2013	20.369105739311376
2014	21.124995503303122
2015	20.927840618816123