Year	Percent
1977	15.66147
1978	28.13065
1979	25.31955
1980	27.29137
1981	34.60925
1982	43.89377
1983	37.23396
1984	33.71906
1985	32.00944
1986	34.30131
1987	36.80161
1988	31.92338
1989	26.14939
1990	27.55488
1991	23.49614
1992	24.85148
1993	26.06903
1994	19.32804
1995	16.32127
1996	13.58024
1997	9.47579
1998	10.92261
1999	22.43785
2000	22.94423
2001	33.48243
2002	33.62208
2003	31.35581
2004	31.64142
2005	24.7383
2006	27.60884
2007	15.45373
2008	18.99011
2009	18.11242
2010	18.71402
2011	14.67943
2012	7.60317
2013	7.67869
2014	7.25787
2015	9.68889
2016	12.6071