Year % 1990 25.1743892165122 1991 25.6281336262746 1992 26.0596546310832 1993 26.4771327737702 1994 27.3526615969582 1995 27.7289309682664 1996 27.9974700694447 1997 28.2135630328295 1998 28.415542959643 1999 28.5936160751687 2000 28.7490348092627 2001 28.8967255672528 2002 29.0239807393797 2003 29.1297108416782 2004 29.2174085169494 2005 29.3144105171257 2006 29.3938494133509 2007 29.4404871029358 2008 29.4833585383547 2009 29.4987284062573 2010 29.5288228593797 2011 29.5792626586851 2012 29.6845950823299 2013 29.9041250976448 2014 30.113032436977 2015 30.2133297999205 2016 30.2639355494459 2017 30.357536646154 2018 30.3991249005569 2019 30.4122057347381 2020 30.4410884883131 2021 30.4859554869051 2022 30.5337217872042