Year	Percent
1971	8.14896
1972	10.16907
1973	10.59577
1974	8.13996
1975	6.5397
1976	9.61902
1977	14.31178
1978	11.87698
1979	7.30534
1980	6.87377
1981	4.16924
1982	6.63138
1983	8.00821
1984	10.02398
1985	11.63332
1986	11.73825
1987	10.74435
1988	14.60727
1989	15.91482
1990	13.6479
1991	22.67074
1992	25.70393
1993	26.35348
1994	22.81645
1995	27.47138
1996	28.36893
1997	36.01143
1998	26.85912
1999	34.66023
2000	28.09424
2001	27.22508
2002	29.62787
2003	32.5614
2004	33.66741
2005	35.67518
2006	44.56971
2007	48.92854
2008	42.99834
2009	52.39833
2010	56.74539
2011	46.30144
2012	47.91418
2013	42.78415
2014	36.56526
2015	33.21042
2016	29.6233