I wondered the same thing. For the most important variable in their study they sure don't explain it very well. I looked all over FAOSTAT but couldn't find an

I wondered the same thing. For the most important variable in their study they sure don't explain it very well. I looked all over FAOSTAT but couldn't find an explanation. http://faostat3.fao.org/home/index.html#METADATA http://faostat3.fao.org/home/index.html#METADATA