Year Percent 1990 3.696 1991 3.898 1992 3.909 1993 3.91 1994 3.38 1995 3.42 1996 3.32 1997 3.04 1998 2.58 1999 3.17 2000 2.47 2001 2.36 2002 2.42 2003 2.33 2004 2.33 2005 2.31 2006 2.44 2007 2.72 2008 2.79 2009 3.19 2010 3.15 2011 3.26 2012 3.31 2013 3.78 2014 3.49 2015 4.11 2016 4.56 2017 4.618 2018 4.675 2019 4.733 2020 4.791 2021 4.848 2022 4.906 2023 4.964 2024 5.021 2025 5.079 2026 5.137 2027 5.194 2028 5.252 2029 5.309 2030 5.367