Year	Number of
1990	27.68
1991	27.24
1992	26.41
1993	25.97
1994	26.09
1995	25.62
1996	27.74
1997	29.17
1998	31.4
1999	33.23
2000	36
2001	37.62
2002	39.69
2003	40.45
2004	41.52
2005	42.73
2006	45.56
2007	48.74
2008	51.75
2009	55.14
2010	58.55
2011	62.09
2012	64.55
2013	67.37
2014	69.89
2015	72.7
2016	75.8