Year	Number of
1990	139.71
1991	139.51
1992	139.7
1993	139.65
1994	141.12
1995	143.49
1996	146.82
1997	151.57
1998	157.5
1999	159.51
2000	160.45
2001	160.28
2002	161.45
2003	162.44
2004	163.03
2005	163.92
2006	164.84
2007	166.03
2008	167.31
2009	168.28
2010	170.01
2011	170.88
2012	174.05
2013	175.54
2014	178.02
2015	180.73
2016	184.12