The Informal Economy: Large and Growing in Most Developing Countries
A new study shows the informal sector - where income is unreported and illegal activities such as smuggling and fraud go undetected – is large and growing in many developing countries.
(...) In Africa the informal economy is so large it is more like a parallel economy.
http://rru.worldbank.org/Discussions/Topics/Topic18.aspx

Size and Measurement of the Informal Economy in 110 countries around the World, by Friedrich Schneider
http://rru.worldbank.org/Documents/PapersLinks/informal_econ...