Year	Number of
1990	51.82
1991	50.61
1992	48.7
1993	47.75
1994	48.09
1995	48.75
1996	52.01
1997	53.8
1998	56.96
1999	59.6
2000	63.52
2001	64.59
2002	66.42
2003	67.78
2004	68.43
2005	69.96
2006	73.59
2007	77.9
2008	81.13
2009	85.1
2010	89.17
2011	92.55
2012	93.66
2013	95.5
2014	97.2
2015	99.18
2016	101.47