Year	Number of
1990	47.58
1991	50.83
1992	54.66
1993	58.9
1994	63.25
1995	67.56
1996	70.92
1997	73.99
1998	76.8
1999	79.68
2000	82.82
2001	84.31
2002	85.91
2003	87.62
2004	89.54
2005	91.72
2006	94.54
2007	97.68
2008	101.23
2009	105.09
2010	109.28
2011	112.77
2012	116.49
2013	120.38
2014	124.56
2015	129.05
2016	133.77