Year	% of total
1971	3.3037341502190856
1972	3.4677024284414584
1973	2.161418904304298
1974	1.8382404217632047
1975	2.0611895863685312
1976	1.666055779547499
1977	1.774046647923019
1978	2.7135874530954767
1979	2.3979680376102355
1980	2.4659205050939876
1981	3.1683627898471736
1982	3.0712280309555586
1983	2.427166541533841
1984	2.7114108924689226
1985	2.5536704494996956
1986	3.0594474788252985
1987	2.698063748272521
1988	2.263348639432046
1989	2.5256971059438524
1990	2.1335511464359285
1991	2.425579301723292
1992	2.109774460973309
1993	1.9859034193732736
1994	1.93431035875112
1995	2.003621176991375
1996	2.0928460096540076
1997	2.397867407835523
1998	2.1930206248368287
1999	2.9374156000908234
2000	3.1543951162190824
2001	3.3980907618688128
2002	2.6626474306493746
2003	2.495752582073289
2004	2.7311699741646085
2005	2.665290435274531
2006	2.5039526681404216
2007	2.2684641253338786
2008	2.60782996844949
2009	2.0985967163032777
2010	2.1983732270792737
2011	2.3279430266080183
2012	2.5916355424302964
2013	3.8130191771611073
2014	4.529578380464945
2015	4.7224113387386275