| 1990 | 1991 | 1992 | 1993 | 1994 | 1995 | 1996 | 1997 | 1998 | 1999 | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 | 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | 2019 | 2020 |
| 33,866.60 | 34,474.03 | 34,857.13 | 35,416.31 | 34,892.77 | 36,437.70 | 37,756.70 | 39,362.12 | 41,052.88 | 42,052.10 | 42,627.64 | 43,077.76 | 43,766.18 | 45,807.95 | 47,963.16 | 47,799.05 | 48,708.89 | 48,865.52 | 49,724.93 | 50,645.61 | 49,303.80 | 49,122.01 | 48,491.76 | 45,284.03 | 42,051.52 | 44,824.30 | 44,956.01 | 45,853.88 | 41,857.34 | 40,190.22 | 39,713.28 |