Year	% of total
1971	38.17035488890696
1972	38.671798261686845
1973	30.40403927317326
1974	32.21809946164995
1975	30.083577838331532
1976	30.93788199923862
1977	31.05215469856619
1978	32.3560355804394
1979	28.456884900153394
1980	26.246634418549547
1981	24.720765878962187
1982	21.920060955234373
1983	17.99504137415236
1984	16.22727654714766
1985	14.492348503955037
1986	14.926777442601807
1987	15.634739819583377
1988	14.228967798761136
1989	14.245927344065532
1990	12.515863970595154
1991	11.751054792360554
1992	11.78601155806972
1993	11.29300654272692
1994	9.863646792539358
1995	9.419558750566514
1996	9.50400614936429
1997	8.994662722873146
1998	8.537409801278281
1999	7.662150405190284
2000	6.5813597528651835
2001	7.037945678476889
2002	6.582298537103188
2003	7.4864564114645065
2004	7.070547917415563
2005	8.938244745586687
2006	8.639699801916368
2007	8.404426484576161
2008	4.931887686521299
2009	4.94731152991266
2010	5.4559975055533565
2011	5.396663929495626
2012	5.41244642488474
2013	5.694111440400365
2014	4.793608596580837
2015	4.41570744336693