% 30 25 20 15 10 5 0 24.1% 4.1% 2001 23.4% 4.3% 24.5% 4.8% 2003 27.5% 4.9% 29.1% 5.6% 2005 29.5% 6.3% 29.3% 7.4% 2007 28.9% 9.0% 26.5% 10.6% 2009 25.4% 11.7% 24.7% 11.2% 2011 23.7% 11.2% 21.1% 11.5% 2013 18.3% 12.3% 17.5% 14.7% 2015 16.6% 15.4% 15.3% 16.9% 2017 15.9% 16.6% US China