Year Percent 1990 26.209 1991 26.57 1992 26.829 1993 27.092 1994 27.48 1995 27.812 1996 28.249 1997 28.664 1998 29.187 1999 29.643 2000 30.052 2001 30.515 2002 29.622 2003 32.154 2004 33.234 2005 33.158 2006 32.661 2007 32.178 2008 31.705 2009 31.638 2010 31.573 2011 31.51 2012 30.621 2013 31.007 2014 31.073 2015 31.182 2016 31.237 2017 31.249 2018 31.264 2019 31.281 2020 31.3 2021 31.322 2022 31.345 2023 31.372 2024 31.405 2025 31.444 2026 31.489 2027 31.54 2028 31.595 2029 31.652 2030 31.707