Year Percent 1990 0.797 1991 0.72 1992 0.812 1993 0.915 1994 1.031 1995 1.162 1996 1.309 1997 1.475 1998 1.661 1999 1.87 2000 2.105 2001 2.369 2002 2.664 2003 2.996 2004 3.368 2005 3.784 2006 4.249 2007 4.768 2008 5.347 2009 5.992 2010 6.71 2011 6.56 2012 6.517 2013 6.474 2014 6.432 2015 6.39 2016 6.588 2017 6.812 2018 7.036 2019 7.261 2020 7.485 2021 7.709 2022 7.934 2023 8.158 2024 8.382 2025 8.607 2026 8.831 2027 9.056 2028 9.28 2029 9.504 2030 9.729