Year 1 in: rate varies by country 2000 13 2001 15 2002 15 2003 15 2004 15 2005 16 2006 17 2007 16 2008 16 2009 16 2010 16 2011 17 2012 18 2013 18 2014 18 2015 18 2016 19 2017 17 2018 18 2019 18 2020 19