Year	Percent
1980	12.11339
1981	12.22893
1982	11.87154
1983	12.53646
1984	10.30843
1985	10.56763
1986	10.83888
1987	10.09747
1988	9.83011
1989	9.93085
1990	12.00912
1991	9.52973
1992	9.7338
1993	10.50015
1994	11.64282
1997	10.1955
1998	11.95229
1999	13.16768
2000	13.77486
2001	14.55976
2002	15.72008
2003	15.24438
2004	15.75277
2005	16.52897
2006	15.38131
2007	15.77553
2008	15.49281
2009	14.41753
2010	13.62345
2011	14.22012
2012	13.65146
2013	13.44169
2014	12.76169
2015	12.82486
2016	12.85084