Year	Number of
1990	31.89
1991	33.27
1992	34.63
1993	36.03
1994	37.5
1995	39.11
1996	41.35
1997	43.77
1998	46.34
1999	48.97
2000	51.63
2001	55.59
2002	59.64
2003	63.79
2004	68.2
2005	72.99
2006	76.92
2007	81.14
2008	85.77
2009	90.93
2010	96.72
2011	100.54
2012	104.83
2013	109.38
2014	114.4
2015	119.88
2016	125.89