性行为的发展

在男女相互关系层面，人类的生殖行为是一个日益引起担忧的问题。自两个世纪前从托马斯·马尔萨斯起，人口统计学家就已经对“人口过剩”感到担忧，并且把不断上升的出生率当作一个需要设法处理的问题。尽管马尔萨斯的最为可怕的预言没有成真，他所畏惧的许多人口现象仍就伴随着我们。涉及这个议题的细节讨论远超出了本教程的范围，不过至少其中的一个细节应该在此有所提及：

将来，有一点似乎是确定无疑的，就是最不能供养人口的那些国家会继续有最高的出生率。换一句话说，从世界范围看，贫穷的夫妻比富裕的夫妻会有更多的孩子。换言之：越是高收入国家，那里的孩子就越有较多的机会开发他们的潜力，比低收入的国家有和仍将会有较低的出生率。低收入国家始终缺乏良好的教育水准和充分的就业条件，并且这些匮乏可能更为恶化。要发现这些趋势背后的原因并不难：发达国家的妇女享受着更好的性生活质量，有便利条件使用避孕措施，并因此在寻求自我健康保健时可以避免怀孕。反过来，发展中国家的妇女常常未受教育，受限于做家庭主妇和母亲的辛劳，并且难以获得避孕药具。

除了这些显而易见的、由这种不同的人口增长所产生的经济和环境问题以外，发展中国家在设法控制人口的过程中，它们究竟如何能够做出多大的努力和应该如何做出努力，确实存在疑问。甚至将来也许更难以回答的另一个疑问是：在设法控制贫穷国家的人口中，富裕国家如何能够做出多大的努力和应该如何做出努力？

低收入               中等收入            高收入      1980 - 1998年   1998 - 2015年

1980-2015年年均人口增长率

本柱形图显示——三类国家人口增长(%)：低收入国家、中等收入国家和高收入国家。不过，因为人口基数的起点较高，在可预见的将来，预期绝对人口数量将会增加。低收入国家和中等收入国家的人口增长率高于高收入国家。 资料来源：世界银行

Stages of Development: Adulthood

Reproductive Behavior 2

On the international level, human reproductive behavior is increasingly causing concern. Beginning with Thomas Malthus about two centuries ago, demographers have been worrying about “overpopulation” and have seen rising birth rates as a problem to be managed. Although Malthus’ most dire predictions have not come true, many of his fears are still with us. A detailed discussion of the issues involved lies beyond the scope of this course, but at least one of them should be mentioned here:
It seems certain that, in the future, those countries that can least afford it, will continue to have the highest birth rates. In other words, world-wide, poor couples will have many more children than rich couples. Putting it still another way: High income countries, where children have a better chance to develop their potential, have and will have much lower birth rates than low income countries, where a good education and good jobs are already scarce and are likely to become scarcer. The reasons behind these trends are not difficult to find: Women in developed countries enjoy greater sexual equality, have easy access to contraception, and thus can avoid pregnancies while pursuing careers of their own. Conversely, women in developing countries are often uneducated, restricted to their roles as housewives and mothers, and have difficulty obtaining contraceptives.
Apart from the obvious economic and environmental problems resulting from this unequal population growth, there is the question of how far countries can and should go in their attempts to control their populations. Even more difficult is another question that may be asked in the future: How far can and should rich countries go in trying to control the populations of poor countries?

Average annual population growth rates 1980-2015

Low income       Middle income     High income   1980 - 1998   1998 - 2015

The chart shows - in percent - the growth of populations in three groups of countries: Low income, middle income, and high income. The growth rates are declining in all three groups. However, the absolute numbers are expected to increase in the foreseeable future, because they start from a larger population base. The growth rates tend to be higher in low- and middle-income countries than in high-income countries.
Source: World Bank