Limao and Venables (2001) emphasize that the quality of transport infrastructure significantly affects countries' ability to trade. They create an infrastructure quality index based on roads, railways and telephone lines coverage for 103 countries, and show that a country that ranks on the 75lh percentile of the index faced 12 per cent higher transport costs than the median country and 28 per cent lower trade. This is due to the increasing importance of global supply chains, just-in-time inventory management and lean retailing. For exporters sourcing intermediate inputs from varied sources, the disruption of one delivery can stymie an entire production process.