Year	%
1988	24.5469
1989	23.38784
1990	28.45542
1991	26.42546
1992	25.2283
1993	24.23119
1994	26.87054
1995	19.97127
1996	18.81352
1997	20.16922
1998	19.05879
1999	19.35946
2000	21.9468
2001	20.72962
2002	19.83016
2003	20.77323
2004	18.23321
2005	15.43066
2006	15.08905
2007	16.59257
2008	18.07278
2009	16.48886
2010	15.75425
2011	15.62757
2012	12.02674
2013	14.59169
2014	13.71038
2015	12.76093
2016	12.94091
2017	10.83129