Without official data or coordinated collection and collation of available information, it is hard to give realistic indications of the situation. However, the UN Development Program 's 1994 Human Development Report ranked Somalia 165th out of 173 countries in terms of its Human Development Index, which combines income levels with educational attainments and life expectancy. According to the World Bank, health standards in Somalia before the 1991 were among the worst in the world. It was estimated that there was 1 doctor for every 20,000 people (in the United States it was 1 doctor for every 470 people), and 1 nurse for every 1,900 persons (in the United States it was 1 nurse for every 70 persons). Only 2 percent of births were attended by a health professional, whereas in the United States nearly 100 percent of births were so attended. In 1990 average life expectancy at birth was 46 years, the infant mortality was about 123 per 1,000 live births (in the United States it is 7 per 1,000). The adult literacy rate was 27 percent.