*Excludes Observations that spanned multiple years

  B
b
t
W
w
 
Pre 1970000000
1970000000
1971000000
1972000000
1973000000
1974000000
1975000000
1976000000
1977001001
1978000000
1979000000
1980000000
1981000000
1982000000
1983001001
1984000000
1985002002
1986004004
1987004004
198800110011
1989007007
1990002002
199100110011
199200170017
1993006006
199400130013
199500130013
199600110011
1997004004
199800100010
1999009009
200000110011
200100100010
200200110011
2003004004
200400100010
200500170017
200600130013
200700230023
200800140014
200900120012
201000100010
201100180018
201200260026
201300300030
201400320032
201500600060
201600640064
201700480048
201800460046
201900620062
2020000000
2021000000
Total0064700647