Year	Number of
1990	39.81
1991	40.08
1992	40.07
1993	40.72
1994	42.42
1995	41.48
1996	43.51
1997	44.71
1998	43.2
1999	45.76
2000	45.91
2001	47.91
2002	49.4
2003	51.93
2004	51.62
2005	52.55
2006	54.6
2007	55.98
2008	55.73
2009	56.43
2010	58.39
2011	60.49
2012	63.19
2013	65.57
2014	66.24
2015	68.73
2016	67.8