Year	Number of
1990	48.68
1991	50.46
1992	52.31
1993	54.12
1994	56.34
1995	59.08
1996	62.9
1997	67.24
1998	71.98
1999	76.93
2000	82.04
2001	85.43
2002	88.9
2003	93.04
2004	97.51
2005	102.52
2006	106.44
2007	110.59
2008	115.37
2009	120.3
2010	125.36
2011	129.53
2012	133.73
2013	137.94
2014	142.29
2015	146.92
2016	151.77