I just tried in vain to find the Garber page referenced to get the  billion figure but I did find a NASA presentation paper report  which gives a different  figure about twice as high  billion  I did a sanity check by looking up the Consumer price index by countryUnited States of America and the curve indicates a rise from  in the s to  in  indexed to  in  a  increase This is consistent with  billion x    billion and would have put the  billion back in the s I will try to fix this when I get a chance