【加賴叫過去】評論

Historically, as countries have developed industrially, they have undergone declines in death rates followed by declines in birth rates. Over time they have tended to move from rapid increases in population to slower increases, then to zero growth and finally to population decreases. The model which demographers use to help explain these changes in population growth is known as the demographic transition model. In order to properly appreciate the demographic transition model, it is necessary to understand two basic concepts: the crude birth rate (CBR) and crude death rate (CDR). The CBR is determined by taking the number of births in a country in a given year and dividing it by the total population of the country and then multiplying the answer by one thousand. So, for example, the CBR of the United States in 2004 was 14 (in other words, there were 14 births per thousand living people in that year). CDR is worked out in a similar way. The CDR for the United States in 2004 was 8 per thousand.選(A)