Year	% of total
1971	58.0952380952381
1972	60.16114592658908
1973	65.36624203821655
1974	64.15770609318996
1975	61.42506142506142
1976	67.49059645351961
1977	74.60172963131542
1978	69.63531669865644
1979	76.81491170699803
1980	74.1399762752076
1981	78.8659793814433
1982	78.37641942498188
1983	60.004647920055774
1984	28.725749559082892
1985	28.060552874067575
1986	19.952114924181963
1987	15.118870728083209
1988	14.447792944513385
1989	14.127231755936903
1990	21.452197196408886
1991	27.229710352738746
1992	30.878265703168427
1993	21.603022534070977
1994	19.388506876227897
1995	38.77090995373116
1996	32.07708779443254
1997	36.94267515923567
1998	40.25711662075299
1999	30.374466433837792
2000	28.298153034300793
2001	36.009049773755656
2002	36.70087483176312
2003	37.80530053698251
2004	42.4265962404847
2005	44.8836291913215
2006	48.30550621669627
2007	43.45834351331542
2008	38.85847903491524
2009	49.1518121600517
2010	54.508175713773134
2011	44.44119937694704
2012	45.130651726703725
2013	51.008125188083056
2014	50.82486526514995
2015	47.197057684862564