Year	Number of
1990	76.61
1991	78.32
1992	79.43
1993	80.02
1994	80.47
1995	81.02
1996	84.95
1997	89.23
1998	94.39
1999	99.97
2000	105.95
2001	113.66
2002	121.82
2003	130.51
2004	139.41
2005	148.49
2006	157.47
2007	166.23
2008	174.78
2009	183.22
2010	191.7
2011	201.71
2012	211.79
2013	222.06
2014	232.64
2015	243.65
2016	256.7