Year	Percent
1971	14.75771
1972	15.42637
1973	14.864
1974	15.20968
1975	18.22086
1976	16.37358
1977	13.11315
1978	19.0047
1979	17.43791
1980	18.26431
1981	18.11682
1982	18.83977
1983	20.29427
1984	24.89685
1985	28.00552
1986	32.02213
1987	35.63602
1989	31.53879
1992	31.48307
1993	31.43209
1994	29.47393
1995	33.50547
1996	41.48333
1997	37.97922
1999	62.66639
2000	64.10187
2001	67.16102
2002	65.62802
2003	71.34306
2004	71.31207
2005	70.1998
2006	68.90088
2007	77.31497
2008	85.26106
2010	73.95371
2011	69.43634
2012	69.42516
2013	70.82767
2014	70.84746
2015	71.32833
2016	72.68963