Year Percent 1973-01-01 15.98740 1974-01-01 7.95377 1975-01-01 9.50709 1976-01-01 10.31220 1977-01-01 14.04420 1978-01-01 17.03780 1979-01-01 17.03780 1980-01-01 17.03780 1981-01-01 17.03780 1982-01-01 17.03780 1983-01-01 17.03780 1984-01-01 17.03780 1985-01-01 17.03780 1986-01-01 17.03780 1987-01-01 17.03780 1988-01-01 17.03780 1989-01-01 17.03780 1990-01-01 17.03780 1991-01-01 17.03780 1992-01-01 17.03780 1993-01-01 17.03780 1994-01-01 17.03780 1995-01-01 17.03780 1996-01-01 17.03780 1997-01-01 17.03780 1998-01-01 17.03780 1999-01-01 17.03780 2000-01-01 17.03780 2001-01-01 17.03780 2002-01-01 61.68410 2003-01-01 55.50180 2004-01-01 46.95230 2005-01-01 42.75730 2006-01-01 41.83130 2007-01-01 45.82920 2008-01-01 49.32450 2009-01-01 73.78320 2010-01-01 69.56070 2011-01-01 67.99790 2012-01-01 78.42150 2013-01-01 85.14410 2014-01-01 88.60880 2015-01-01 120.07900 2016-01-01 147.64500