Can I determine my ancestor’s year of birth from their age in a census?
Yes, but with reservations! At first you might assume that if for example, your ancestor was aged 20 in the 1851 census, they must have been born in 1831 because simple arithmetic tells you that 1851 minus 20 equals 1831. If the census had been taken at midnight on 31December 1851, this would be true. However censuses were not taken at the end of the year. So your 20 year old ancestor may have been born in 1830 rather than 1831. In fact most censuses were taken around the end of March or the start of April, so the majority of people were born later in the year than the date of the census. This makes the odds roughly 3:1 that a person aged 20 on the night of the 1851 census was actually born in the last three quarters of 1830 rather than the first quarter of 1831. (So an easy rule of thumb for estimating the most probable birth year by subtraction is to treat the census as being in 1850, 1860 etc. Then you don’t have to remember whether you should be adding or subtracting one!)
If you want to aim for precision the following are the dates of the principle censuses of interest to UK family historians:
1841 – Sunday 6 June
1851 – Sunday 30 March
1861 – Sunday 7 April
1871 – Sunday 2 April
1881 – Sunday 3 April
1891 – Sunday 5 April
1901 – Sunday 31 March
1911 – Sunday 2 April
All of the above assumes that your ancestor has correctly told the enumerator their age but this is not necessarily the case. Ages can be recorded wrongly for the reasons discussed near the top of this page. Finally ages in the 1841 census can cause further confusion for the reasons described in the following section.
My ancestor’s age in 1841 seems wrong
The method of recording ages in the 1841 census is a source of great confusion, not least to some of the enumerators who conducted the census! The instructions given to the enumerator were: “Write the age of every person under 15 years of age as it is stated to you. For persons aged 15 years and upwards, write the lowest of the term of 5 years within which the age is.” So if the age appearing in this census is 35 for example, you should expect the true age of the person to be anywhere between 35 and 39. The instructions go on to give some examples which should have made things clear but some enumerators still got it wrong. The most common “mistake” is to ignore the instructions altogether and record exact ages, which is great for us, as family historians. The fact that the adult ages are not multiples of 5 years gives a clue when this is happening, but even this should be treated with caution. I have come across one enumerator who consistently subtracted exactly 5 years from every age!
My ancestor’s birthplace in 1841 seems wrong
The 1841 census did not record actual birthplaces. The only indication is a column headed: “Where born – Whether in the same County.” and another headed “Whether born in Scotland, Ireland or Foreign Parts”. For the first of these, the instructions given to the enumerator were: “Write opposite to each name (except those of Irish, Scotch or Foreigners) “Y.” or “N.” for Yes or No as the case may be.” For the second, the instructions were: “Write in this column, “S.” for those who were born in Scotland; “I.” for those born in Ireland; and “F.” for Foreigners. This latter mark to be used only for those who are subjects of some Foreign State, and not for British subjects who happen to have been born abroad.”
Nowhere does this answer the question “Whether in the same county as what, or whom?” The intention was that the “Y” and “N” should indicate the birth county relative to the county in which the person was now living, but this is not clearly stated and a high proportion of the letters are wrong. Some enumerators seem to have interpreted it as “in the same county as the head of the household” or as “in the same county as the previous person entered in the schedule.” Note also that a correctly entered “N”, with the second column left blank, can indicate a British subject born in Buckinghamshire, Wales, or Timbuktu, but not in Scotland or Ireland! A correctly entered “Y” indicates that the person was born in Oxfordshire, but not necessarily (as is assumed by some beginners) that they were born in the actual town or village where they were living in 1841.
My ancestor seems to be missing in 1841
During the summer months, some agricultural workers lived in temporary field shelters. The 1841 census was held on 7th June by which time these people were away from home and so “escaped” the attention of the census enumerator. Later censuses were held earlier in the year at the end of March or the beginning of April, partly to avoid this problem.
My ancestor seems to be missing in 1861Oxfordshire
The census enumerators’ books for 1861 for the Woodstock sub-district, are missing. So if your ancestor lived within this area (which extended as far south as Kidlington and Wolvercote), they will not appear in the 1861 census.