Year including construction (constant 2010 US$) 1991 16347.5435282583 1992 15744.1443558153 1993 16434.8459204963 1994 16623.2248358762 1995 16463.0523974555 1996 16406.4581960692 1997 16914.1104608311 1998 16613.938902924 1999 16629.451377823 2000 14965.2878544082 2001 14942.951991992 2002 13726.8795913732 2003 13541.7245212447 2004 14287.2156493135 2005 15877.105587653 2006 23582.1259204319 2007 20265.599778413 2008 20210.2920785006 2009 19361.7555871537 2010 18994.1519268664 2011 19123.1662987379 2012 18921.3851470271 2013 19913.8956302503 2014 19977.890390561 2015 19027.4756115646 2016 18407.5207870128 2017 17668.662197491 2018 16743.6917907038