Year	Number of
1990	88.58
1991	86.3
1992	83.91
1993	80.5
1994	79.23
1995	78.63
1996	77.8
1997	81.12
1998	79.69
1999	83.01
2000	85.61
2001	91.77
2002	101.48
2003	107.46
2004	114.39
2005	120.16
2006	125.08
2007	132.06
2008	135.67
2009	139.96
2010	144.09
2011	147.6
2012	149.86
2013	150.85
2014	152.41
2015	156.03
2016	161.59