Year	Number of
1990	77.75
1991	77.38
1992	76.89
1993	76.18
1994	78.43
1995	80.32
1996	86.29
1997	91.79
1998	97.18
1999	99.27
2000	102.21
2001	101.2
2002	101.65
2003	98.99
2004	99.96
2005	100.73
2006	103.49
2007	107.94
2008	112.78
2009	117.83
2010	122.58
2011	126.8
2012	130.48
2013	134.23
2014	137.34
2015	141.19
2016	145.19