Public international law concerns the structure and conduct of sovereign states; analogous entities, such as the Holy See; and intergovernmental organizations. To a lesser degree, international law also may affect multinational corporations and individuals, an impact increasingly evolving beyond domestic legal interpretation and enforcement. Public international law has increased in use and importance vastly over the twentieth century, due to the increase in global trade, environmental deterioration on a worldwide scale, awareness of human rights violations, rapid and vast increases in international transportation and a boom in global communications.