Year	Number
1991	17.67076
1994	20.61326
1996	19.0061
1997	15.96615
1998	15.9995
1999	16.07076
2001	20.3441
2002	20.34332
2003	18.8372
2004	20.26241
2005	21.19732
2006	21.24161
2007	19.3076
2018	15.41859