*Excludes Observations that spanned multiple years

  B
b
t
W
w
 
Pre 1970000000
1970000000
1971000000
1972000000
1973000101
1974000000
1975000000
1976000000
1977000000
1978000000
1979000000
1980000000
1981000000
1982000000
1983000000
1984000000
1985000000
1986000011
1987000101
1988000101
1989000000
1990000000
1991000101
1992000000
1993100001
1994100001
1995000101
1996000101
1997000101
1998000000
1999000101
2000000000
2001000000
2002000101
2003000000
2004000000
2005000101
2006000000
2007000101
2008000202
2009000000
2010000000
2011000000
2012000000
2013000101
2014000101
2015000202
2016000000
2017000000
2018000000
Total20017120