Year	Number of
1990	141.51
1991	145.04
1992	150.09
1993	156.68
1994	158
1995	163.69
1996	168.17
1997	175.19
1998	180.7
1999	180.29
2000	182.81
2001	182.43
2002	187.07
2003	189.86
2004	192.28
2005	191.47
2006	192.02
2007	193.54
2008	198.13
2009	203.88
2010	210.09
2011	214.12
2012	219.17
2013	224.81
2014	230.41
2015	236.25
2016	241.55