Year	Number of
1990	34.7
1991	35.19
1992	35.7
1993	36.17
1994	36.8
1995	37.52
1996	38.29
1997	39.28
1998	40.3
1999	41.79
2000	43.43
2001	44.36
2002	45.37
2003	46.45
2004	47.49
2005	48.74
2006	50.13
2007	51.71
2008	53.29
2009	55
2010	56.89
2011	58.85
2012	60.96
2013	63.21
2014	65.66
2015	68.31
2016	71.1