Year	Units
1968-01-01	5306.79011509404
1969-01-01	6066.17273858960
1970-01-01	5013.99150019507
1971-01-01	3926.26491936295
1972-01-01	6222.73945143320
1973-01-01	6671.79838922667
1974-01-01	7333.42903275210
1975-01-01	6316.93978319218
1976-01-01	7846.41478785323
1977-01-01	6383.92888803131
1978-01-01	6238.40835600776
1979-01-01	5167.17481746461
1980-01-01	4187.22835906956
1981-01-01	2878.10851982654
1982-01-01	2248.42860205021
1983-01-01	1917.43597644240
1984-01-01	2299.88923411675
1985-01-01	2515.97466141962
1986-01-01	2452.14022178591
1987-01-01	3108.29725777736
1988-01-01	3755.50791752203
1989-01-01	4166.72537076084
1990-01-01	4248.19447024358
1991-01-01	3867.99570318102
1992-01-01	4139.12119825113
1993-01-01	4561.54727308826
1994-01-01	4624.90033987216
1995-01-01	3679.16852393240
1996-01-01	4033.62056009314
1997-01-01	4189.67623569619
1998-01-01	3136.71715887140
1999-01-01	3796.71213931902
2000-01-01	3587.46836722348
2001-01-01	3444.53473496386
2002-01-01	3528.42788075399
2003-01-01	3756.52840443604
2004-01-01	4322.40113330016
2005-01-01	4945.73645250168
2006-01-01	5103.34644773465
2007-01-01	4514.50061044407
2008-01-01	4405.58649526471
2009-01-01	3826.96445099866
2010-01-01	4153.69740682342
2011-01-01	3726.65206738109
2012-01-01	3891.48152505776
2013-01-01	4121.92502001543
2014-01-01	4510.19046500964
2015-01-01	3861.27458843784
2016-01-01	4216.68590246509
2017-01-01	4225.52597189891