Year	Percent
1980	1.295
1981	0.715
1982	0.894
1983	0.796
1984	0.861
1985	0.91
1986	0.818
1987	0.668
1988	0.779
1989	1.015
1990	0.874
1991	0.988
1992	0.99
1993	1.062
1994	1.019
1995	0.895
1996	0.979
1997	1.653
1998	4.873
1999	4.386
2000	3.0274
2001	2.7389
2002	2.2226
2003	2.6257
2004	2.687
2005	2.8896
2006	2.4808
2007	2.4084
2008	2.3615
2009	2.7494
2010	2.925
2011	2.852
2012	2.6185
2013	2.5595
2014	3.2603
2015	3.1974
2016	3.2081
2017	3.3108