Year	Percent
1978-12-31	11.7129
1979-12-31	13.4746
1980-12-31	16.8781
1981-12-31	13.5648
1982-12-31	12.336
1983-12-31	10.1411
1984-12-31	9.8266
1985-12-31	12.4492
1986-12-31	10.8839
1987-12-31	9.6476
1988-12-31	9.6315
1989-12-31	13.5497
1990-12-31	14.7466
1991-12-31	11.7958
1992-12-31	9.6242
1993-12-31	5.9475
1994-12-31	5.0881
1995-12-31	6.3293
1996-12-31	5.9356
1997-12-31	6.5658
1998-12-31	7.2512
1999-12-31	5.2543
2000-12-31	5.8876
2001-12-31	4.9996
2002-12-31	3.8631
2003-12-31	3.5989
2004-12-31	4.3723
2005-12-31	4.6562
2006-12-31	4.6928
2007-12-31	5.6265
2008-12-31	4.7689
2009-12-31	0.6694
2010-12-31	0.5231
2011-12-31	0.6011
2012-12-31	0.5484
2013-12-31	0.4751
2014-12-31	0.4685
2015-12-31	0.4498
2016-12-31	0.3765