there's an underlying assumption, which is lightly supported by anecdotal accounts
those members of the households on migration are not included in feeding ...
SJA: Aug 27, 2007
now introducing the fertility rate and
declining of age into fertility with age
TODO: we need to introduce a sigmoid for a gradual decline in the
fertility of women
Reference: www.bcm.edu/news/item.cfm?newsID=66
TODO: to get a proper reference