*Excludes Observations that spanned multiple years

  B
b
t
W
w
 
Pre 1970000000
1970000000
1971000000
1972000000
1973000000
1974000000
1975000000
1976000000
1977000000
1978000000
1979001001
1980000000
1981000000
1982000000
1983000000
1984000000
1985000000
1986000000
1987000000
1988000000
1989001001
1990000000
1991000000
1992000000
1993000000
1994000000
1995000000
1996000000
1997000000
1998000000
1999000000
2000000000
2001000000
2002000000
2003000000
2004000000
2005000000
2006000000
2007000000
2008000000
2009000000
2010000000
2011000000
2012000000
2013000000
2014000000
2015000000
2016000000
2017000000
Total002002