Year	% of total
1971	88.60698535002788
1972	83.09583553949216
1973	83.86669231920307
1974	82.72390037095919
1975	82.57478453491186
1976	86.08622524285174
1977	84.38805172240971
1978	83.48144113298575
1979	82.5373846888331
1980	81.27463473905699
1981	81.84008668624712
1982	82.80084733466818
1983	85.7130657557643
1984	84.1963525751043
1985	82.29830961597371
1986	85.67794589151806
1987	84.868447696316
1988	80.38288946124639
1989	81.96727795282858
1990	82.25598283288498
1991	74.31825783849445
1992	78.30611680044285
1993	76.86026389790179
1994	76.33850841555426
1995	71.82870448486484
1996	72.0603096984515
1997	59.89360957513824
1998	54.768580828473155
1999	53.681719581936505
2000	61.0390110524897
2001	62.1857943786433
2002	60.60655887457751
2003	67.05114254624593
2004	60.946211437370565
2005	56.62733745139953
2006	61.73341627191093
2007	61.55043536069269
2008	56.201120758667415
2009	52.711245042517454
2010	47.33829327438592
2011	54.737979644832976
2012	55.095790655732124
2013	45.73083230832308
2014	40.48648814453544
2015	42.59579503049058