Regrettably the surviving census returns are not a full record of the population of nineteenth century England and Wales, and it may not always be possible to track down individuals, addresses and householdld These omissions reflect both under-enumeration at the time of the census, and subsequent loss or damage to the returns.
In the early censuses under the GRO, certain groups, usually those not living in conventional households, were simply not enumerated by name. These included the members of the Royal Navy on board ship in 1841, and possibly in 1851; all members of the merchant marine in 1841, and various sections of it thereafter, all fishermen afloat in 1841, and sections of this group thereafter; the crews of vessels engaged in inland navigation in 1841 and 1851; and all itinerants, travellers and night workers in 1841, and probably a considerable number of the same in later years. The soldiers serving abroad were never enumerated by name.
Undoubtedly, some individuals and households that should have been enumerated will have completely slipped through the census net. Some of these omissions might reflect clerical error as enumerators and households made inevitable slips in the recording or copying. A house might have been omitted, perhaps because it was unoccupied on census night, and the enumerator forgot to note it down as empty; a wife might have been absent because of an enumerator’s copying blunder; an elderly visitor might have been temporarily lost sight of; and so on. But in some districts, or among some social groups, it might have been difficult for hard-pressed enumerators to ensure that they had handed a household schedule to every family.
In the absence of any detailed research on the subject it is difficult to put a figure to such levels of under-enumeration. It should be noted, however, that post-enumeration surveys for the 1981 census indicated that 0.5% of households were missed in that census in the whole of England and Wales.
Some of the original returns, which were not always kept in optimum archival conditions in the nineteenth century, have been lost or damaged. Often such damage was confined to the backs and fronts of enumerators’ books, but more extensive gaps exist. Special returns, such as those for shipping, were often appended to the back of enumerators’ books, were especially liable to damage. In the 1851, all the ship returns seem to have been destroyed.
Making Sense of the Census Revisited by Edward Higgs. Copyright TNA
As far as the COCP knows, no large sections of the Cornish returns are missing, just odd pages here and there. Also, Cornwall was free of large urban districts, which are particularly hard to enumerate. However, the Cornish would have been heavily represented in the maritime returns that were not taken or which were lost in the earlier years.