Year	Number of
1990	26.7
1991	27.48
1992	28.25
1993	28.9
1994	29.49
1995	30.03
1996	30.53
1997	30.95
1998	31.38
1999	31.89
2000	32.51
2001	33.34
2002	34.25
2003	35.25
2004	36.33
2005	37.5
2006	38.4
2007	39.28
2008	40.41
2009	41.65
2010	43.05
2011	44.85
2012	46.79
2013	49.06
2014	51.43
2015	53.94
2016	56.85