Year	%
1988	73.08099
1989	63.65615
1990	63.80539
1992	79.01504
1993	49.91554
1994	51.94585
1995	39.12228
1996	29.6878
1997	36.09452
1998	38.66572
1999	38.90274
2000	46.1652
2001	36.54414
2002	40.01194
2003	42.13921
2004	34.55707
2005	22.92585
2006	21.97922
2007	21.30371
2008	22.09957
2009	20.89526
2010	21.69276
2011	19.65229
2012	14.56656
2013	16.60171
2014	21.11589
2015	16.19283
2016	17.39769
2017	14.02641