Year Percent change (Units) 1999 -1.111 2000 -4.231 2001 -0.454 2002 -7.704 2003 -16.224 2004 -6.270 2005 -7.413 2006 -3.556 2007 -3.401 2008 -16.323 2009 7.396 2010 19.683 2011 14.197 2012 16.658 2013 1.975 2014 2.394 2015 1.794 2016 0.756 2017 5.176 2018 4.987 2019 -6.307 2020 -7.782 2021 8.425 2022 6.485 2023 5.313 2024 3.196 2025 3.219 2026 3.141 2027 3.062 2028 3.021 2029 3.003