Year Percent 1990 3.682 1991 3.45 1992 3.295 1993 3.147 1994 3.005 1995 2.87 1996 2.74 1997 2.896 1998 3.062 1999 3.236 2000 3.42 2001 3.614 2002 3.818 2003 4.034 2004 4.261 2005 4.5 2006 4.136 2007 3.8 2008 3.1 2009 5 2010 3.2 2011 2.811 2012 2.468 2013 2.166 2014 1.9 2015 2 2016 2.3 2017 2.227 2018 2.153 2019 2.08 2020 2.006 2021 1.933 2022 1.86 2023 1.786 2024 1.713 2025 1.639 2026 1.566 2027 1.493 2028 1.419 2029 1.346 2030 1.273