Year Percent 1990 3.17 1991 3.06 1992 3.16 1993 3.13 1994 2.43 1995 3.01 1996 3.17 1997 3.2 1998 3 1999 2.77 2000 2.96 2001 2.95 2002 3.03 2003 3.33 2004 3.06 2005 3.26 2006 3.74 2007 4.08 2008 4.35 2009 4.1 2010 4.38 2011 4.55 2012 4.47 2013 4.91 2014 5.01 2015 5.61 2016 5.82 2017 5.914 2018 6.008 2019 6.101 2020 6.195 2021 6.289 2022 6.383 2023 6.477 2024 6.57 2025 6.664 2026 6.758 2027 6.852 2028 6.946 2029 7.039 2030 7.133