Year	Number of
1990	51.85
1991	51.4
1992	50.62
1993	49.25
1994	50.58
1995	51.28
1996	54.82
1997	57.3
1998	59.6
1999	62.58
2000	67.14
2001	68.16
2002	71.75
2003	71.43
2004	74.21
2005	76.48
2006	79.8
2007	84.79
2008	89.35
2009	93.82
2010	97.92
2011	101.29
2012	104.13
2013	107.09
2014	109.74
2015	112.77
2016	116.26