The national estimate is for 9.7 billion pounds, slightly less than last year's.
"There really is a concern when we translate that small sample into a national estimate," he said.
According to national estimates, approximately 40 to 50 percent of summer water use is for the outdoor landscape.
But no one forced the argument into the open by calling for a national estimate or a broader discussion of the threat.
There is no official national estimate of how many adults have the operation each year.
It was perhaps inevitable that the national estimate on Iraq's weapons programs would receive special scrutiny.
The 1997 update was the last national estimate on the terrorism danger completed before 9/11.
The national estimate has often played this role, and is sometimes controversial for this very reason.
These cases provided the basis for the national estimates presented in table 2.
In the Sudan - the only country that already had reliable national estimates - it is 9 out of 10.