The Population Registers were the equivalent to the UK’s National Register; but unlike the UK, several were compiled during The Emergency (as the war was referred to in Ireland). This appears to have been because the Population Register was not updated, but static. Thus changes of address and births and deaths necessitated the collection of up-to-date data.
The first were compiled in 1941 and then subsequent canvasses were taken in 1943, 1947 and possibly 1951. The data noted was each person’s name, occupation and date of birth. The data was collated by address on the night of the canvas. However, unlike the UK, where an individual was away from home on the set night their permanent address was recorded too.
Despite making extensive enquiries I have been unable so far to establish the fate of the Population Registrars and it seems likely that they have been destroyed. Assumedly, each earlier register was pulped after the subsequent one was compiled.
Although they were not census enumerations, the system followed for gathering the data was borrowed from the census. All personal data was noted on ‘Form As’, which were household schedules, and statistics and lists of the household returns (noting each head of household’s name) were recorded by street or townland on ‘Form Bs’.
Enquiries have established that the Central Statistics Office retains some – possibly all – of the statistical ‘Form Bs’ but not the vital ‘Form As’.
i hope this helps.