Year	Number of
1990	251.18
1991	253.25
1992	257.14
1993	259.91
1994	263.59
1995	269.79
1996	267.31
1997	269.65
1998	271.63
1999	273.3
2000	274
2001	283.45
2002	294.93
2003	306.66
2004	318.94
2005	332.75
2006	339.51
2007	346.86
2008	356.28
2009	365.67
2010	377.14
2011	390.81
2012	405.36
2013	420.53
2014	436.06
2015	452.57
2016	468.72