The construction industry globally, contributes between 18% and 24% of the GDP, and because of its labour intensive characteristics, contributes handsomely to total employment, forming important backward and forward linkages with the rest of the economy. Nevertheless, the extent and sophistication of these linkages crucially depend on the relative development of the construction industry relative to the overall economy. In the developing countries, these linkages are not very strong because of the use of informal materials, which is not commercialised and whose opportunity costs are often zero, and the huge imports of construction materials used in the modem sector of the economy.