Year	% of total
1971	21.99753239441508
1972	21.975807914627605
1973	22.227915154440268
1974	22.105960006237964
1975	23.179311739341905
1976	20.732355941347745
1977	22.902476774212964
1978	22.465672256004403
1979	19.505406665005726
1980	18.79618518912503
1981	20.742492158805597
1982	22.076293177351157
1983	11.528898372045074
1984	16.422810139504705
1985	19.586089888771223
1986	17.446689474183117
1987	20.368205852760475
1988	15.141112700143013
1989	18.4330526501297
1990	18.23596639824397
1991	16.56255890307677
1992	16.088695064864527
1993	17.408749075187977
1994	17.611051149592516
1995	18.785931818167768
1996	19.323344400116568
1997	20.491291772364303
1998	26.621831334842117
1999	25.87802463548259
2000	28.350210934161584
2001	32.17571931415458
2002	36.02899109338567
2003	36.76213635378133
2004	36.92010970193083
2005	37.60250499515649
2006	43.034322716470754
2007	45.75724713375999
2008	42.95207947949224
2009	46.00239359289838
2010	49.677788407457115
2011	49.82103971882386
2012	52.616002197044494
2013	52.49759344138217
2014	52.54306012926313