Year	Number of
1990	72.08
1991	75.28
1992	78.85
1993	82.72
1994	86.99
1995	91.69
1996	90.16
1997	88.85
1998	87.63
1999	86.38
2000	85.08
2001	86.06
2002	86.81
2003	87.76
2004	88.84
2005	90.14
2006	93.41
2007	97.16
2008	101.37
2009	106.07
2010	111.26
2011	115.92
2012	120.92
2013	125.89
2014	130.96
2015	136.17
2016	141.79