The economic interdependence of different countries, as well as advancements in communication technology, and the progress of technology, in general, have all contributed to globalization. There are many theories of globalization. Let's look at World-systems theory first. World-systems theory focuses on the importance of the world as a unit, rather than looking at individual countries. It divides the world into three regions: core countries, periphery countries, and semi-periphery countries. Core countries include areas like Western Europe and the United States. These countries have a strong central government with enough tax to support it. They are economically diversified, industrialized, and relatively independent of outside control. They have strong middle and working classes and focus on higher scope production of material goods rather than raw materials. Periphery countries are those in Latin America and Africa and tend to have a relatively weak government. They tend to depend on only one type of economic activity like extracting raw materials.