Year	Number of
1990	26.65
1991	26.76
1992	26.88
1993	27.04
1994	27.25
1995	27.52
1996	27.98
1997	28.51
1998	29.03
1999	29.53
2000	30
2001	30.49
2002	30.96
2003	31.56
2004	32.18
2005	32.84
2006	33.47
2007	34.12
2008	34.9
2009	35.73
2010	36.62
2011	37.47
2012	38.38
2013	39.23
2014	40.14
2015	41.13
2016	42.04