Year	Percent
1970-01-01	3.73927872194897
1971-01-01	4.17532522050375
1972-01-01	4.04517513252882
1973-01-01	8.26666666600004
1974-01-01	14.24893553825680
1975-01-01	9.66969548151244
1976-01-01	11.25614250621110
1977-01-01	11.98928332210510
1978-01-01	9.71603274954341
1979-01-01	7.73923642806676
1980-01-01	10.42269995291260
1981-01-01	11.27215970794350
1982-01-01	8.33125575581155
1983-01-01	5.49366551432092
1984-01-01	8.11639795517100
1985-01-01	4.38934095741536
1986-01-01	6.16438356164368
1987-01-01	4.08911644641213
1988-01-01	5.99925074273700
1989-01-01	5.54145981508565
1990-01-01	8.03956867283909
1991-01-01	9.02909418116381
1992-01-01	7.59204836795523
1993-01-01	8.06352808952712
1994-01-01	5.12713521698837
1995-01-01	6.74106761623137
1996-01-01	4.46630617999246
1997-01-01	3.55029585798825
1998-01-01	3.12536579655860
1999-01-01	2.64862252295820
2000-01-01	1.81294613887087
2001-01-01	1.74665224985432
2002-01-01	1.83299389002050
2003-01-01	1.98196734627542
2004-01-01	3.12226204699354
2005-01-01	3.10496640148300
2006-01-01	3.48340699677866
2007-01-01	4.16782961611569
2008-01-01	11.27066523808480
2009-01-01	2.92089711805365
2010-01-01	3.91304347826083
2011-01-01	4.52421150505276
2012-01-01	3.73120950756887
2013-01-01	2.96013449689034
2014-01-01	2.64629146477823
2015-01-01	1.58404616052259
2016-01-01	2.18686161532911
2017-01-01	1.59716060337177