Year Number 1995 16652119.272753762 1996 16883667.810397737 1997 18570111.722413797 1998 19110481.739070974 1999 20547389.638149675 2000 22028654.63923025 2001 22699583.121966902 2002 23251643.310645618 2003 23525106.48666884 2004 25484888.26690859 2005 25761318.527669124 2006 27999916.146485254 2007 30898966.037649684 2008 32780642.470848747 2009 32486504.558505412 2010 37843566.163916536 2011 33747412.9930026 2012 36199883.00667659 2013 39516963.59896522 2014 42941757.49010313 2015 43653648.12222777 2016 46851127.10151834 2017 49979552.76387189 2018 51524462.8351512 2019 51930012.46659737