Year	Number of
1990	150.13
1991	160.56
1992	169.84
1993	178.16
1994	185.76
1995	191.82
1996	203.39
1997	214.8
1998	226.82
1999	239.17
2000	253.01
2001	267.74
2002	286.48
2003	305.22
2004	322.52
2005	340.94
2006	358.32
2007	372.4
2008	386.64
2009	402.6
2010	418.46
2011	435.31
2012	451.69
2013	467.37
2014	482.11
2015	494.35
2016	505.93