Infant mortality is one of the most important indicators of the health of a nation, as it is associated with a variety of factors such as maternal health, quality and access to medical care, socioeconomic conditions, and public health practices. The U.S. infant mortality rate generally declined throughout the 20th century. In 1900, the U.S. infant mortality rate was approximately 100 infant deaths per 1,000 live births, while in 2000, the rate was 6.89 infant deaths per 1,000 live births. However, the U.S. infant mortality rate did not decline significantly from 2000 to 2005, which has generated concern among researchers and policy makers.