Year	Percent
1971	22.70003
1972	35.56077
1973	43.20233
1974	24.31895
1975	14.99731
1976	19.72365
1977	17.51032
1978	22.15077
1979	15.92145
1980	9.55107
1981	9.13103
1982	4.2332
1983	4.60652
1984	11.46057
1985	11.15253
1986	7.46424
1987	6.75202
1988	7.72155
1989	8.42101
1990	8.30973
1991	7.74014
1992	18.33518
1993	22.30132
1994	25.38259
1995	32.2074
1996	33.08835
1997	26.23804
1998	18.38326
1999	14.82664
2000	13.6139
2001	15.59684
2002	16.31089
2003	20.89683
2004	23.98568
2005	28.56126
2006	44.17989
2007	75.6292
2008	73.69387
2009	84.69324
2010	81.61692
2011	87.12131
2012	84.71025
2013	74.17158
2014	65.28222
2015	65.59932
2016	67.18438