Year	% of total
1971	0.4627821848126549
1972	0.4930618062473655
1973	0.46555519025983677
1974	0.2949083843559027
1975	0.3021177916383184
1976	0.33386699479734894
1977	0.2666066588056047
1978	0.2757715895540712
1979	0.3897005110174784
1980	0.35908393668720756
1981	0.7342437522646083
1982	0.8610891187633812
1983	0.8242278365238456
1984	0.6018352771974887
1985	0.6353286808634879
1986	0.7142973937254237
1987	0.7452990176573948
1988	0.7265440746221012
1989	0.6966425644505084
1990	0.9355153592690967
1991	1.0267942787523043
1992	0.911991563810638
1993	0.9193875092628567
1994	0.9142606924892444
1995	1.0031698725137368
1996	1.1649191523416367
1997	1.2325261959116636
1998	1.777747387374063
1999	2.518782324768598
2000	2.9323632742020163
2001	3.0917446727171636
2002	2.891146441770578
2003	2.6676762748578926
2004	2.7194416581823977
2005	2.7877553793674203
2006	3.7453086504122957
2007	4.4788494077842165
2008	4.658195543227568
2009	5.471076692669536
2010	5.348165632878282
2011	5.633276556471005
2012	6.14661434289476
2013	5.814139705512596
2014	5.703830938674734
2015	5.624531035904593