Year	Number of
1990	57.33
1991	60.24
1992	61.23
1993	63.25
1994	62.28
1995	62.75
1996	63.01
1997	64.45
1998	68.36
1999	73.65
2000	78.98
2001	80.86
2002	84.45
2003	89.15
2004	93.29
2005	95.94
2006	97.59
2007	106.31
2008	114.83
2009	124.26
2010	129.16
2011	134.57
2012	138.34
2013	144.15
2014	143.51
2015	145.75
2016	148.71