This book explores the notion of a technological system and more specifically the distinction between modern and traditional technological systems. Using highly disaggregated data for a range of sectors and developing countries we have applied this distinction to micro - as well as macro-economic policy issues. By identifying distinct systems of technology in a multisectoral model of the economy we have been able to quantify certain aspects of those systems within a rigorous conceptual framework. The relationship between income distribution, the choice of technology and its subsequent impact is examined in detail.