Year	Number of
1990	79.59
1991	77.45
1992	75.14
1993	72.35
1994	71.16
1995	70.46
1996	70.05
1997	72.81
1998	72.52
1999	76.38
2000	79.79
2001	85.89
2002	94.52
2003	100.67
2004	107.28
2005	112.91
2006	116.9
2007	122.18
2008	124.96
2009	127.65
2010	129.93
2011	131.47
2012	131.91
2013	131.67
2014	132
2015	134.32
2016	137.51