Our lives are full of what ifs, and the two questions above have occurred to me from time to time. There is, though, another form of "what it" questions that are or should be more sensibly considered than these flights of fancy. They are those relating to opportunity cost, the alternatives we forgo when we take a certain course. The question arose this week, as I write in my column today, when a friend asked if I'd ever considered the opportunity cost of alcohol. He had in mind other things I could have spent that money on, and certainly over a few decades of imbibing there's serious money involved. But no regrets there.

The opportunity costs that interests me more are the different courses my life may have taken if I had not been predisposed towards a few beers. And on reflection I think that like Bob Hawke and Winston Churchill I have taken more out of booze than booze has taken out of me. I do, however, regret drinking too much when I shouldn't have, and I'm not alone in that. And I do regret drinking too freely when I was in my 20s, as many men in their 20s do and as I suspect many of them regret decades later.

There are many decisions that should be made in the light of opportunity costs. Having children should be preceded by an assessment of opportunity cost, and I suspect that it is only ever assessed carefully by the people who decide not to have children!

And what of the opportunity cost of working for money for most of our adult life? Does anyone ever consider that?

What's your take on opportunity cost?