Year	Number of
1990	47.82
1991	49.48
1992	51.59
1993	53.85
1994	56.68
1995	59.4
1996	62.2
1997	65.11
1998	68.56
1999	72.1
2000	76.4
2001	81.11
2002	85.37
2003	89.95
2004	95.33
2005	100.24
2006	104.19
2007	108.72
2008	113.54
2009	118.92
2010	124.53
2011	129.6
2012	135.25
2013	141.43
2014	147.63
2015	154.28
2016	162.56