Year	% of total
1971	29.28304183087945
1972	29.683570945024655
1973	30.700268092146025
1974	30.702247636466474
1975	26.637394441878552
1976	27.31077098514161
1977	30.21892939040273
1978	31.34557380844235
1979	34.33670792721867
1980	37.44826766045497
1981	33.28776942529832
1982	29.26485045455888
1983	27.490395446349414
1984	30.24975888321787
1985	30.081804147502105
1986	23.58023842065174
1987	25.14390480306711
1988	26.513746893073463
1989	26.06837762041697
1990	27.86725738547758
1991	28.593104086883482
1992	30.947504092277377
1993	31.69115918384981
1994	35.56152207023332
1995	36.61796528558188
1996	37.706984402383966
1997	38.25351653867179
1998	42.21660727096013
1999	40.310146358276846
2000	42.276665140309355
2001	43.244445272952184
2002	44.300872782612466
2003	42.48637456046541
2004	42.97532709340748
2005	44.16831872432729
2006	43.187095603072365
2007	43.40464972235694
2008	40.36716288441306
2009	39.049302829479764
2010	32.660355748393535
2011	30.921072247740618
2012	30.87615771671607
2013	32.6537067630652
2014	37.37859696344222