Year	% of total
1971	81.53386454183267
1972	86.3541468969444
1973	86.31744919411352
1974	86.2934042199701
1975	87.56830601092896
1976	88.51980542043086
1977	88.20246593121351
1978	87.75341819896275
1979	88.70453095086151
1980	89.47842626889579
1981	90.2127659574468
1982	90.16437861271676
1983	90.0623268698061
1984	90.27743877634042
1985	90.28608902369047
1986	90.55859137826351
1987	90.811447068344
1988	90.44147985146472
1989	91.06240566966336
1990	87.61315228966986
1991	86.63093530610705
1992	72.61223782284625
1993	69.4146518814761
1994	69.69494358545758
1995	71.34601492896702
1996	70.27802961619824
1997	77.97257175173193
1998	75.13429459994344
1999	73.22660778360475
2000	65.75971261309206
2001	64.93888489443755
2002	41.66507420854831
2003	39.2662871600253
2004	41.384162722271974
2005	49.46551948898449
2006	58.89853664460502
2007	55.07830231502496
2008	58.48181458227275
2009	52.02999887222285
2010	52.57228257745589
2011	56.03603603603604
2012	56.43585847623183
2013	58.7251828631139
2014	60.363523701332234
2015	60.50867507886435