Year % 1990 27.269866848121083 1991 27.49002734488786 1992 28.12344233681253 1993 28.436196120460302 1994 28.558002828806995 1995 28.776724846282885 1996 28.944704415924715 1997 28.887135152078116 1998 28.95793586213168 1999 28.79030637821636 2000 29.070758688396193 2001 29.52221256939505 2002 29.399709072673613 2003 29.387705772006107 2004 29.23111455484912 2005 29.217421451498478 2006 28.874305777397627 2007 28.736495645861016 2008 28.638369380976027 2009 28.477214536188356 2010 27.990800822189968 2011 27.78323010832437 2012 27.552500186188745 2013 27.371658981112674 2014 27.240964075498354 2015 27.021862176282507 2016 26.981962028167345 2017 26.82321292321185 2018 26.74483587880547 2019 26.69703057035475 2020 26.58296428939821 2021 26.53043321551205