Those same forces also contributed to a massive increase in services trade, though from a much smaller base, as global sourcing of and foreign investment in services have both surged. Furthermore, while both low- and middle-income countries have made substantial progress in dismantling their trade barriers over the past two decades, this has not appeared to unleash sustained export growth in all of them (World Bank, 2007). Such heterogeneity of outcomes is the main underlying reason why there is no consensus in the literature about the quantitative impact of trade liberalisation on economic growth (see Box 1). Trade, growth and poverty reduction: where do we stand?