Year	Percent
1971	23.44947
1972	25.60154
1973	26.64307
1975	29.2564
1988	39.43536
1989	36.28947
1990	35.78156
1991	34.60662
1992	31.05399
1993	32.28881
1994	29.9382
1995	28.5977
1996	30.19941
1998	30.37719
1999	33.8689
2000	36.86344
2001	36.69522
2002	36.63128
2003	40.46083
2004	46.59435
2005	58.13786
2006	56.8664
2007	60.89558
2008	67.33498
2009	74.16131
2010	71.0383
2011	71.6342
2012	70.46016
2013	69.68234
2014	70.17874
2015	70.73861
2016	69.75856