Year	Percent
1971	7.28075
1972	8.74458
1973	8.81326
1974	8.49779
1975	8.9742
1976	9.78656
1977	10.84549
1978	13.41008
1979	11.99422
1980	16.77638
1981	18.23365
1982	22.05529
1983	23.87295
1984	25.8914
1985	24.99536
1986	27.60646
1987	29.4582
1989	19.17266
1990	21.56175
1991	21.60629
1992	22.74739
1993	19.34765
1995	17.00946
1996	13.97853
1997	22.18013
1998	23.40857
1999	24.24622
2000	22.11735
2001	23.39798
2002	25.27594
2003	24.16187
2004	32.20652
2005	35.61033
2006	38.62547
2007	46.93285
2008	44.16703
2009	46.68495
2010	45.26044
2011	50.5545
2012	53.81896
2013	53.33637
2014	64.63839
2016	77.64084