Year Percent of GDP (Units) 1997 21.103 1998 17.567 1999 21.807 2000 24.344 2001 28.243 2002 27.896 2003 30.267 2004 31.563 2005 32.185 2006 31.414 2007 30.274 2008 31.470 2009 34.828 2010 35.007 2011 36.460 2012 37.322 2013 37.012 2014 35.606 2015 34.059 2016 33.481 2017 32.631 2018 32.031 2019 30.842 2020 30.251 2021 28.356 2022 25.607 2023 23.152 2024 20.614 2025 18.408 2026 16.412 2027 14.580 2028 12.891 2029 11.390