Year	Number of
1990	64.84
1991	65.11
1992	66.29
1993	67.55
1994	69.34
1995	71.52
1996	74.48
1997	76.69
1998	81.5
1999	84.51
2000	86.5
2001	85.59
2002	85.54
2003	88.14
2004	91.14
2005	94.36
2006	98.1
2007	101.5
2008	104.43
2009	107.89
2010	110.91
2011	114.14
2012	119.87
2013	125.82
2014	132.42
2015	139.01
2016	144.94