As we saw earlier, death rates and birth rates have been nearly equal throughout much of human history. However, in Western Europe, death rates began to fall in the 17th and 18th centuries but birth rates were still high therefore the population increased. However, birth rates also began to decline and today birth rates and death rates are nearly equal in Europe. This decline in death rate followed by decline in birth rate leading to low population growth is called demographic transition. These declines in birth and death rates were generally concurrent with economic development in European nations. Thus this transition also refers to changes in economics from primarily agrarian to a more urban, commercial and eventually industrial system. An understanding of demographic transition is useful to see clearly what has brought about the rapid growth of world population especially in the last 50 years.