One important set of constraints arises from the nature of their integration with the global economy. Since LDCs tend to be open economies that rely heavily on primary commodity and low value added manufactures exports, and that are dependent on various forms of capital inflows to support the balance of payments, they are often disproportionately affected by changes in global trade and capital flows, as well as by flows in cross-border migration. National policies are thus strongly conditioned by the external environment and must also be able to respond to that environment flexibly, which often makes it more difficult to pursue them in a systematic and planned manner.