(b) Accentuation of housing difficulties. The latter has become for the German authorities a first class problem owing to the already existing acute shortage of accommodation, clothes, furniture and labour. There is no doubt that after a very heavy raid industrial efficiency is seriously affected in consequence of the preoccupation of those who have been bombed out with their own personal affairs. 5. A by-product of all raids has been loss of sleep. If carried out often enough, nuisance raids as well as medium and heavy raids have this effect in areas which are liable to heavy attack.