性行为的发展

在世界范围内，首次性交的平均年龄现在介于17-18岁之间，并且在一些西方国家，这个年龄甚至低许多。这个平均年龄的准确统计数据在国与国之间有差异，但是，存在向低年龄发展的趋势。在上个世纪50年代，首次性交的平均年龄仍旧是21岁左右，不过始终在降低。60年代避孕药的引入和70年代的“性革命”恰好又加强了这种下降的趋势。我们必须牢记全世界的女孩和男孩都在越来越早的年龄就进入了青春期，而且在许多国家，结婚的年龄一直在往上提升。换一个角度说，这就意味着年轻人不大可能等到结婚之后才开始发生性交。考虑到这一点，现时的统计数据几乎不会令人感到吃惊。

首次性交[1]平均年龄(女孩与男孩)
在经过挑选的国家统计  资料来源: 2004年杜雷斯全球性调查[2]

首次性交[1]平均年龄(女孩与男孩)

在经过挑选的欧洲国家统计 资料来源：2006年国际计划生育联合会(IPPF)欧洲互联网统计

[1].这里的性交指的是本教程所定义的“性交合（coitus）”。——译者注。

[2].生产性生活用品的杜蕾斯，会经常进行全球的“性调查”。参见网文：被争议的杜蕾斯全球性调查，网站：三联生活周刊；http://qkzz.net/magazine/1005-3603/2005/43/266727.htm (2008-12-11)

Stages of Development: Adolescence

Erotic Behavior 3

World-wide, the average age of the first sexual intercourse now lies between 17 and 18 years, and in some Western countries it is much lower. The exact figures vary from one country to another, but there is a general trend towards an earlier start. In the 1950’s, the average age of first coitus was still around 21 but already then began to fall. The introduction of the contraceptive pill in the 1960’s and the “sexual revolution” in the 1970’s only reinforced this tendency. One also has to keep in mind that all over the world both girls and boys reach puberty at an ever earlier age, and that in many countries the age of marriage keeps going up. This means, among other things, that young people are less likely to wait until they are married before they begin sexual intercourse. In view of this, the current statistics are hardly surprising.

Average age of first sexual intercourse (girls and boys)
In selected countries
Source: Durex Global Sex Survey 2004

In selected European countries
Source: IPPF European Network 2006