The World Bank has often been quoted that disaster risk reduction saves $7 (sometimes $4-7) for every $1 invested. Extensive effort from several colleagues has been unable to track down the original study. The World Bank no longer uses this ratio and recommends against quoting it.
The earliest source for the ratio that we found is the 1995 paper at http://onlinelibrary.wiley.com/doi/10.1111/j.1467-7717.1995.tb00338.x/abstract stating (p. 183) "The World Bank and U. S. Geological Survey calculate that a predicted $400 billion in economic losses from natural disasters over the 1990s could be reduced by $280 billion with a $40 billion investment in prevention, mitigation and preparedness strategies." No reference is given. The paper was so long ago that the authors understandably cannot assist further.
I seek your help:
1. To check if the 7:1 ratio originates from the $280 billion / $40 billion figures or other calculations.
2. To find the original World Bank / USGS study with the $280 billion / $40 billion numbers or with the 7:1 ratio.
I am aiming to update the document at http://www.ilankelman.org/miscellany/MitigationSaves.rtf with the wealth of recent studies that have emerged on this topic. Thank you for any time and help. And please do not use the 7:1 ratio until we have solved the mystery!
Ilan