December-May

As you may know, Older woman and younger man relationship is become more of a vogue these days. There are a lot of celebrity couples like this, to name a few, Demi Moore and Ashton Kutcher. Susan Sarandon and Tim Robbins. Anjali and Sachin Tendulkar.
It seems almost one-third of women between ages 40 and 69 are dating younger men (defined as 10 or more years younger). According to a recent AARP poll, one-sixth of women in their 50s, in fact, prefer men in their 40s.
Tina B. Tessina, Ph.D., a licensed family therapist in practice in Long Beach, Calif., and author of "The Unofficial Guide to Dating Again", tells WebMD that

It's not what you think -- the stamina or "re-boot" ability of the younger male. The women like the flexibility and sense of adventure of their more spontaneous, younger companions

Though this is spreading slowly, its still not being accepted easily in the society.
Why is that the man needs to be older than the woman? Does it really matter who is older in a relationship?
I had one such conversation with my friends recently, so one of my friend was saying that women think matured sooner than men and thats why it is preferred to have the an older man and younger woman relationship. But I was not convinced with the explanation. So when I gave a little thought on this, I was wondering if this trend of older man and younger woman was due to the patriarchy that existed across the World. Due to the patriarchy, they wanted the men to be in full control always and it was easier to achieve if the man was older than the woman. Now that woman are becoming more independent the patriarchy is reducing and thus older woman and younger man relationship has started blooming.
After this thought I was even more curious about the reason and so tried searching the Internet. That is when I came across this Fertility and evolutionary psychology theory in Wikipedia. As per that article women begin to lose their fertility as they enter their late thirties. While men remain fertile until much later in life, although it declines over time. The evolutionary psychology suggests that people are more likely to be attracted to people who look like they might be fertile. But all these being said, I feel these theories would have evolved in recent years. But older man and younger woman relationship has been followed for many years. So I feel my reasoning more convincing than these. What do you think?
Interestingly, there seems to be a folk formula that has been evolved to compute correct disparities of age between older and younger partners, this being "divide by two and add seven", else the relationship is liable to be subject to moral disapprobation. I feel the age disparities suggested by this formula seems more.

Sources: MSN, Wikipedia

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