Women tend to laugh more than men because the two genders communicate in slightly different ways. Whether men are really from Mars and women from Venus is another matter entirely. The fact is that women have more ability to recognise non-verbal body language and the tone of a persons voice than men do. This leads women to understand more when light hearted communication is needed, and when another person could benefit from laughter as a response to their communication.
We learn early on in the dating game that women prize the ability of a man to make them laugh above looks and other factors which come into the art of attraction. Men often add humor into their sexual repertoire and understand that if they can make a woman laugh then she is more likely to find them attractive.
Likewise women learn that men enjoy them laughing at their jokes. To not laugh at the appropriate moment would cause disappointment and may even be regarded as an insult on occasion. What can develop because of this is that men tell jokes in order to attract women and women respond by laughing in order not to offend the men, even if the joke wasn't very funny. This in itself is fairly amusing.
Women may also laugh on other occassions as a form of smoothing over a situation and making those around them more relaxed. A woman may use laughter in this manner as a way of making others feel good, which is what women are automatically taught to do from a young age.
On top of these reasons for women to laugh more than men sits one more reason. This is that if women didn't laugh at life then they would probably suffer too much stress. Women have to be emotionally pretty tough. This is hard for the fairer sex because they have to endure rather allot in life that usually wouldn't be regarded as being funny at all.
However, the innate ability to laugh at what life has to throw at them means that women can benefit from the feel good factor that comes from laughing. When we laugh healing chemicals are released into our bloodstreams. This is why it is often recommended to people who are ill or depressed to seek our laughter and humor in order to get better faster.
If women didn't laugh as much as they do then the their stress levels would go through the roof, making them sick and lowering their immune systems. You only have to witness a woman who isn't laughing enough to see that this is so. When stress gets on top of a woman she becomes weak, unless she fights it off with laughter as her best defense.