*Excludes Observations that spanned multiple years

  B
b
t
W
w
 
Pre 19708000210
1970200002
1971300003
1972100001
1973200002
1974300003
1975100001
1976100001
1977300003
1978000000
1979100001
1980000000
1981200002
1982100102
1983000000
1984000000
1985200204
1986000000
1987000101
1988000101
1989100326
1990000145
1991000404
19922007413
199330042330
19941008148157
19952004157163
19962004132138
199720063947
19983001168172
199900011415
20001007200208
200100056671
20020005129134
200310053743
20041004149154
200510054753
200600022224
2007000112738
200800052429
200900012012
201000018725
201100021526
201200004343
201300003131
201400014748
2015000202
2016000044
2017000000
2018000000
Total500015115311732