Year	Number of
1990	38.77
1991	38.32
1992	38.08
1993	37.69
1994	37.74
1995	38.1
1996	38.82
1997	39.67
1998	40.53
1999	39.72
2000	40.09
2001	41.24
2002	41.96
2003	42.17
2004	43.65
2005	45.32
2006	46.55
2007	48.24
2008	50.2
2009	51.86
2010	53.49
2011	54.97
2012	55.75
2013	56.31
2014	57.41
2015	58.9
2016	62.26