Year	Number
1974	30.96406
1975	36.46885
1976	39.9042
1977	37.17805
1987	36.83118
1988	30.93262
1989	32.50298
1990	34.67047
1991	32.15176
1999	25.23286
2000	24.27274
2001	23.68731
2002	23.53391
2003	21.25328
2004	22.11032
2007	23.82133
2015	11.51072
2016	10.74003
2017	10.50702
2018	10.80498