Year	Number of
1990	182.85
1991	183.3
1992	183.65
1993	180.02
1994	178.96
1995	174.27
1996	173.11
1997	167.71
1998	163.83
1999	158.65
2000	153.7
2001	153.92
2002	150.68
2003	147.76
2004	147.01
2005	143.83
2006	140.6
2007	139.18
2008	137.81
2009	134.61
2010	133.6
2011	134.3
2012	134.95
2013	133.95
2014	134.78
2015	138
2016	140.7