Year	Percent
1968-01-01	0.991721150238533
1969-01-01	0.926556713499223
1970-01-01	0.930422315015739
1971-01-01	1.001474258568130
1972-01-01	1.146398914870420
1973-01-01	1.041349846952100
1974-01-01	1.175616464393620
1975-01-01	1.667423557555350
1976-01-01	1.809603075916540
1977-01-01	1.778352070991130
1978-01-01	2.009284782228580
1979-01-01	1.866542772937750
1980-01-01	1.803777700420010
1981-01-01	1.971160348817840
1982-01-01	2.080343890149260
1983-01-01	2.396622406318010
1984-01-01	2.406566598910870
1985-01-01	2.322721071041820
1986-01-01	2.428724598887560
1987-01-01	2.500207108949260
1988-01-01	2.181398442195840
1989-01-01	1.928893585557390
1990-01-01	1.774296505145570
1991-01-01	1.742191377466390
1992-01-01	1.810906458219150
1993-01-01	2.102327762261500
1994-01-01	2.477886400690790
1995-01-01	2.692884401033020
1996-01-01	2.867478192003430
1997-01-01	2.923095293887470
1998-01-01	3.596621806336300
1999-01-01	4.082268614298270
2000-01-01	4.175000891771800
2001-01-01	4.471751581774180
2002-01-01	4.834219429907870
2003-01-01	4.709684739138940
2004-01-01	4.203409495883890
2005-01-01	3.984330151036180
2006-01-01	3.727724537980220
2007-01-01	3.451910478801540
2008-01-01	3.653664551743890
2009-01-01	4.665400468053320
2010-01-01	4.645845946726790
2011-01-01	4.253639280307240
2012-01-01	4.013665123202650
2013-01-01	3.779079452534900
2014-01-01	3.339777257553370
2015-01-01	3.159510797883100
2016-01-01	2.941902871074180
2017-01-01	2.658720595942390