Year	Number of
1990	33.34
1991	33.62
1992	34
1993	34.66
1994	33.82
1995	35.07
1996	31.9
1997	35.38
1998	35.64
1999	35.68
2000	38.48
2001	39.83
2002	42.24
2003	41.97
2004	39.09
2005	40.06
2006	39.12
2007	40.86
2008	41.93
2009	45.23
2010	46.73
2011	47.44
2012	51.47
2013	54.39
2014	54.72
2015	55.54
2016	57.15