Year	Percent
1960	13.90135
1961	12.88889
1962	13.85281
1963	17.2549
1964	14.9635
1965	11.51316
1966	7.8125
1967	8.90208
1968	8.57909
1969	6.95444
1970	5.76441
1993	16.05707
1994	25.79196
1995	31.18418
1996	25.36401
1997	33.61694
1998	31.23815
1999	40.54419
2000	49.52278
2001	52.54125
2002	55.42213
2003	56.52047
2004	63.6059
2005	64.08471
2006	68.59325
2007	65.32597
2008	65.54325
2009	49.22076
2010	54.08278
2011	54.08076
2012	57.88976
2013	62.38794
2014	62.60347
2015	61.71842
2016	61.28152
2017	60.73397