Niger is a developing country, which consistently ranks near the bottom in the United Nations' Human Development Index (HDI); it was ranked 187th of 188 countries for 2015 and 189th out of 189 countries in the 2018 and 2019 reports. Many of the non-desert portions of the country are threatened by periodic drought and desertification. The economy is concentrated around subsistence agriculture, with some export agriculture in the more fertile south, and export of raw materials, especially uranium ore. Niger faces serious challenges to development due to its landlocked position, desert terrain, inefficient agriculture, high fertility rates without birth control and resulting overpopulation, the poor educational level and poverty of its people, lack of infrastructure, poor healthcare, and environmental degradation.