Year	Number of
1990	59.01
1991	60.71
1992	63.7
1993	66.89
1994	70.51
1995	73.76
1996	76.52
1997	79.44
1998	82.8
1999	84.62
2000	86.58
2001	88.21
2002	91.4
2003	94.67
2004	98.45
2005	101.81
2006	103.78
2007	106.36
2008	109.23
2009	113.18
2010	118.29
2011	122.49
2012	127.71
2013	132.76
2014	138.09
2015	143.38
2016	148.68