Year	% of total
1971	34.02859920716155
1972	34.19719657846746
1973	32.71510626896635
1974	32.35066459940885
1975	31.593239416819458
1976	32.22791853354883
1977	32.240168356414536
1978	32.87994300306456
1979	33.90601517165615
1980	34.38248814345448
1981	36.34767131502411
1982	36.28228618791917
1983	36.356607730903775
1984	39.206323178854205
1985	39.59376049231325
1986	39.70207648488237
1987	39.855961664394265
1988	39.887020717105585
1989	39.94445219767512
1990	44.61184163859672
1991	46.81155580739175
1992	51.1971560466331
1993	55.436031302532896
1994	55.68278871339215
1995	56.09250828618971
1996	56.62903919379468
1997	57.150583453142275
1998	58.25310834919048
1999	57.91635117395227
2000	57.82635210566633
2001	58.481929033381086
2002	58.8882219204084
2003	58.70372605745452
2004	59.024685388406105
2005	61.61747445607227
2006	62.28435042109247
2007	60.06182916220766
2008	58.81910208573603
2009	59.54140164401308
2010	58.70578246127196
2011	60.1081909763779
2012	60.83602818305705
2013	59.859043100815924
2014	61.90282903693164
2015	63.21609334483451