Year	Number of
1990	61.57
1991	63.88
1992	67.73
1993	71.04
1994	74.73
1995	79.23
1996	80.49
1997	83.94
1998	86.78
1999	89.57
2000	93.18
2001	97.95
2002	100.52
2003	103.29
2004	106.91
2005	110.59
2006	115.74
2007	118.83
2008	122.5
2009	125.87
2010	129.1
2011	134.61
2012	140.49
2013	147.43
2014	154.64
2015	162.4
2016	170.61