Year	% of total
1971	34.93799433649058
1972	30.673506222095565
1973	31.719274103380062
1974	31.57284256108877
1975	29.703812543500113
1976	31.424193783744347
1977	30.22874746018221
1978	29.297932384956514
1979	29.092344119968427
1980	29.022791744106424
1981	30.196852288588342
1982	30.804255702822108
1983	32.34664920323074
1984	31.580612002846525
1985	30.629589592574646
1986	26.992864424057082
1987	25.70403530494968
1988	25.327153762268267
1989	22.982556476980267
1990	23.615809885304067
1991	24.317383076507166
1992	31.334992714910147
1993	26.746025571202576
1994	21.507401772561522
1995	23.59537409869838
1996	17.00797933674646
1997	28.35556551956059
1998	30.25369178341537
1999	20.1391807949185
2000	24.47536231884058
2001	25.66180194282031
2002	23.495848319346386
2003	21.211404997743923
2004	18.34912206601098
2005	19.830343484911694
2006	19.39923742211476
2007	18.466608720846008
2008	15.989130823411635
2009	27.12208437592959
2010	27.879308023694133
2011	16.53471026965003
2012	20.449805896884726
2013	26.00132454144951
2014	25.96168932121921
2015	31.763188779576048