Year	Percent
1971	58.67553
1972	53.38703
1974	48.12992
1975	48.54383
1976	50.06048
1977	51.90782
1978	52.48437
1979	52.8648
1980	54.771
1981	57.08537
1991	57.51034
1992	59.61504
1999	64.13401
2000	67.2058
2001	64.34486
2002	65.97168
2003	71.43104
2004	63.86221
2005	71.93615
2006	69.12697
2007	73.50866
2008	78.98618
2009	78.55486
2011	86.20729
2012	105.35369
2013	95.05362
2014	94.09996
2015	99.85143
2017	95.08137