This document discusses human population growth trends over time. It notes that the global human population reached 1 billion in 1830, 2 billion in 1930, 3 billion in 1960, 4 billion in 1975, 5 billion in 1987, 6 billion in 1999, and 7 billion in 2011. It also provides estimates of current birth and death rates worldwide. The document then discusses factors that have allowed unprecedented human population growth, such as advances in agriculture, medicine, and public health. It examines some potential problems associated with high population growth, especially in developing countries, including environmental degradation and resource scarcity. Finally, it outlines the demographic transition process and considers predictions for future global population size and stability.