Year	Percent
1971	55.2081
1972	59.08805
1973	59.33472
1974	63.78942
1975	67.85819
1976	71.98912
1977	75.43966
1978	77.77348
1979	74.82501
1980	73.21998
1981	74.63627
1982	79.06899
1983	81.05295
1984	82.34043
1985	84.90395
1986	86.63461
1987	86.99683
1988	86.89729
1989	89.70003
1990	89.89821
1991	91.45559
1992	95.83913
1993	88.01277
1994	90.17561
1995	89.59484
1996	91.35092
1997	91.27106
1998	91.19591
1999	91.77103
2000	91.24835
2001	92.73814
2002	95.00732
2003	106.04669
2004	107.36376
2005	108.77353
2006	108.63437
2007	105.99396
2008	104.38602
2009	103.5995
2010	104.09681
2011	107.86498
2012	109.40199
2013	65.83269