Year	Number of
1990	67.6
1991	70.12
1992	72.55
1993	74.9
1994	77.33
1995	80.13
1996	82.6
1997	85.11
1998	87.93
1999	90.94
2000	93.77
2001	97.61
2002	101.86
2003	105.57
2004	109.86
2005	114.46
2006	118.87
2007	123.23
2008	127.61
2009	132.02
2010	136.39
2011	140.75
2012	145
2013	149.07
2014	153.68
2015	158.28
2016	163.27