Year	Number of
1990	35.03
1991	35.61
1992	36.5
1993	37.7
1994	39.34
1995	39.53
1996	37.3
1997	41.08
1998	39.97
1999	41.17
2000	42.24
2001	42.7
2002	43.48
2003	44
2004	45.66
2005	46.06
2006	46.76
2007	48.61
2008	49.44
2009	50.48
2010	50.73
2011	50.51
2012	51.34
2013	51.26
2014	51.87
2015	53.87
2016	55.21