Year Percent 1990 22.764 1991 22.782 1992 23.4 1993 18.023 1994 21.715 1995 17.097 1996 22.314 1997 20.357 1998 18.531 1999 16.834 2000 15.263 2001 15.521 2002 15.782 2003 16.047 2004 16.316 2005 16.589 2006 16.864 2007 17.144 2008 17.427 2009 17.714 2010 19.3 2011 21.2 2012 20.1 2013 21.8 2014 23.1 2015 22 2016 20.7 2017 20.977 2018 21.254 2019 21.531 2020 21.808 2021 22.085 2022 22.362 2023 22.639 2024 22.915 2025 23.192 2026 23.469 2027 23.746 2028 24.023 2029 24.3 2030 24.577