El-hadj M. Bah The University of Auckland   Department of Economics The University of Auckland 12 Grafton Rd Auckland, Select State 1142 New Zealand   e.bah@auckland.ac.nz   http://homes.eco.auckland.ac.nz/ebah002/           JEL Areas: O : Economic Development, Technological Change, and Growth E1 : General Aggregative Models: General