Now some part of these involuntary losses, whilst they are unavoidable, arebroadly speakingnot unexpected; such as losses through the lapse of time irrespective of use, and also 'normal' obsolescence which, as Professor Pigou expresses it, 'is sufficiently regular to be foreseen, if not in detail, at least in the large', including, we may add, those losses to the community as a whole which are sufficiently regular to be commonly regarded as 'insurable risks'.