Developed by several demographers in the 1950s, the demographic transition stands as an important alternative to neo-Malthusian notions of population growth. Essentially, it is a model of a society's fertility (birth rate, BR), mortality (death rate, DR), and natural population growth rates (NGR) over time, using the simple relationship NGR = BR–DR. Because this approach is explicitly based on the historical experience of Western Europe and North America as they went through the Industrial Revolution, “time” in this conception is a proxy for industrialization. This approach can be demonstrated with a graph of birth, death, and natural growth rates over time that divides societies into four major stages (Figure 1).