Year	Number
1972	5.75
1973	5.92683
1974	7.11765
1975	4.45745
1977	12.22581
1985	11.65248
1989	9.06687
1997	10.78977
2000	14.42787
2001	14.43499
2003	8.9228
2004	9.51936
2005	9.47397
2008	9.38705
2009	8.59781
2011	10.87494
2015	26.38549