Year	Number of
1990	35.29
1991	33.74
1992	31.4
1993	29.41
1994	28.21
1995	27.21
1996	27.61
1997	28.14
1998	28.84
1999	29.52
2000	30.39
2001	31.99
2002	33.78
2003	35.77
2004	37.91
2005	40.18
2006	41.69
2007	43.11
2008	44.52
2009	45.89
2010	47.27
2011	48.99
2012	50.69
2013	52.46
2014	54.26
2015	56.16
2016	58.34