Year	% of total
1960	3.8381853902482588
1961	3.685650335737379
1962	4.078439876701932
1963	3.4564807253681753
1964	3.5726923631407193
1965	3.1067632031382426
1966	4.209548952926436
1967	4.301600498856787
1968	5.818178294949182
1969	5.292303762361785
1970	4.892871858261228
1971	2.2207876049063913
1972	2.705871809042974
1973	3.114316684732761
1974	2.728124109287837
1975	5.263482830056661
1976	8.646149471823367
1977	6.824161301664667
1978	6.345923902055811
1979	6.1944480136760545
1980	5.028505401310268
1981	4.845938062295339
1982	6.591466566937622
1983	7.580964860168009
1984	13.846890378320603
1985	13.560363702211955
1986	14.225363297069801
1987	16.002662739797874
1988	16.154267776172208
1989	16.845230910363806
1990	18.62986577338644
1991	16.63637736954621
1992	15.932239926707027
1993	18.186079319210904
1994	17.83859403689779
1995	19.799969666840802
1996	20.96550514206468
1997	24.86289367363827
1998	27.944649228282508
1999	33.551136911534975
2000	37.54894588076654
2001	38.31934503887545
2002	35.82073418560743
2003	40.974157986293044
2004	43.87494632780778
2005	50.28365449400351
2006	51.37589334754673
2007	56.01352272063642
2008	55.08265635814459
2009	51.07565852220507
2010	51.12175464315718
2011	48.07881642319257
2012	43.41031557561773
2013	37.81576817675029
2014	33.66832544693581
2015	39.37321087362641