I Need an Explanation

One of life's greatest mysteries to me is this...

Why do I run out of shampoo and conditioner at different times? I use both every day and use about the same amount of both. Ian has his own, so I know this problem is only due to me. I need an explanation! Is it because one is denser and the other fluffier? It just bugs me. Part of the reason it bugs me is that the stores over here always put them on special if you buy more then one. I then end up with odd backlogs of one or the other. I almost want to be SO ANAL that I measure out each one every day just to see if there really is the same amount in each bottle. I know I won't do this though, as it is hard enough for me to bath every day, so adding on top of that measuring my soaps, it would probably send me over the edge into the never bathing territory and that just isn't a good place for me...people then don't want to be my friend!

I then think to myself, life must not be all that bad if this is the type of thing I worry about! And I consider that a good thing.