Year	Number of
1990	51.42
1991	45.82
1992	41.3
1993	39.74
1994	39.62
1995	41.97
1996	43.98
1997	46.32
1998	50.7
1999	54.81
2000	57.97
2001	63.21
2002	63.91
2003	64.19
2004	68.43
2005	73.26
2006	76.56
2007	85.2
2008	93.43
2009	97.56
2010	99.49
2011	99.42
2012	101.05
2013	103.71
2014	117.06
2015	129.99
2016	144.75