Year	Number of
1990	71.7
1991	72.86
1992	73.87
1993	74.93
1994	76.22
1995	77.61
1996	79.93
1997	82.32
1998	85.18
1999	88.56
2000	91.81
2001	94.86
2002	98.11
2003	101.84
2004	106.85
2005	111.31
2006	118.88
2007	124.17
2008	132.26
2009	141.83
2010	151.72
2011	164.29
2012	174.87
2013	186.11
2014	198.17
2015	211.17
2016	225.38