Year	Number of
1990	51.29
1991	52.23
1992	53.24
1993	54.31
1994	55.5
1995	56.84
1996	58.33
1997	60.01
1998	61.85
1999	63.82
2000	65.94
2001	67.38
2002	68.94
2003	70.63
2004	72.48
2005	74.55
2006	76.88
2007	79.43
2008	82.25
2009	85.34
2010	88.71
2011	91.49
2012	94.57
2013	97.87
2014	101.43
2015	105.23
2016	108.91