Germany is a great power with a strong economy; it has the largest economy in Europe, the world's fourth-largest economy by nominal GDP, and the fifth-largest by PPP. As a global leader in several industrial, scientific and technological sectors, it is both the world's third-largest exporter and importer of goods. As a developed country, which ranks very high on the Human Development Index, it offers social security and a universal health care system, environmental protections, and a tuition-free university education. Germany is a member of the United Nations, NATO, the G7, the G20, and the OECD. It has the third-greatest number of UNESCO World Heritage Sites.