Year	Percent
1981	2.48361
1982	2.81346
1983	5.63082
1984	10.98128
1985	11.19948
1986	8.4803
1987	11.8684
1988	8.57776
1989	9.54419
1990	6.63259
1991	6.43131
1992	6.05501
1993	7.50977
1994	7.54352
1995	6.34503
1996	5.63947
1997	7.84105
1998	6.9836
1999	6.89263
2000	7.37808
2001	14.2077
2002	10.24996
2003	13.19084
2004	13.46602
2005	12.91068
2006	13.42239
2007	13.28031
2008	12.26647
2009	14.17532
2010	9.2015
2011	9.06132
2012	12.59991
2013	11.31325
2014	9.15255
2015	8.31365
2016	9.13244