Year	Number of
1990	41.61
1991	43.26
1992	45.02
1993	46.93
1994	48.96
1995	51.14
1996	53.83
1997	56.73
1998	59.9
1999	63.35
2000	67.12
2001	70.93
2002	75.05
2003	79.56
2004	84.42
2005	89.68
2006	94.09
2007	98.72
2008	103.76
2009	109.27
2010	115.4
2011	121.08
2012	127.3
2013	133.84
2014	141.12
2015	149.22
2016	158.45