"Well we have a new study ... that addresses this topic. The authors used thousands of people to get at the answer to your question. And the answer is -- if we could have a drum roll -- is that people are happiest both when they are very young and they are very old. They are least happy when they are in middle age, and specifically the authors found people are the least happy when they are in their 40s.

"Now let's try to make sense of this. Why? Why would you be least happy in your middle age years and happier on the two sides of that?" asks Walden, a professor of agricultural and resource economics. "Well I think there are several possibilities. Certainly people think about when they are young, you were carefree (with) no responsibilities. Perhaps that would contribute to young people being happy.

"Also when you are very old, you can perhaps reflect back on your achievements. Your children are grown and gone, and you can enjoy, for example, your grandchildren. Life is perhaps less hectic. Maybe you've come to terms with who you are. And all of those factors perhaps contribute to your being happy," he continues.

"On the other hand, when you are in middle age you've got a lot going on, you've got a lot of responsibilities. Your income may be high but again you have a lot of demands on those incomes. That may reduce your level of happiness. So this is a very interesting study. It certainly doesn't fit everyone, but I think it does give us cause for reflection."