Year including construction (constant 2010 US$) 1991 27795.0859688707 1992 27878.1227813934 1993 28320.1116752351 1994 25373.8873416724 1995 26334.0227161758 1996 26786.9356436391 1997 29087.3951992006 1998 30294.6759522412 1999 29210.9718931491 2000 28518.0006002052 2001 26867.008279635 2002 26694.7555464216 2003 24877.6912289354 2004 24426.3329686407 2005 25967.0394826856 2006 26211.2943817967 2007 22278.4973084375 2008 22606.7903684029 2009 24693.8575231036 2010 25888.1763779562 2011 24350.2641699713 2012 22500.6512178721 2013 21332.4580861455 2014 21981.1718316945 2015 22362.5511980768 2016 22036.4332696173 2017 22629.6375877648 2018 23820.5007551015