Onenamers (those making a study of a single surname and its variants) are often interested, if only as a rough measure of the likely size of their onename study, to find out how many people bearing the name are alive today. This procedure gives such an estimate for Great Britain.
 Find some organisation with access to the Electoral Registers on CDRom, and plead with them. Remember that the results will be for those of voting age alone, and need to be adjusted by a percentage of those nationally under 17.
 The UKInfo disc claims to contain the Electoral Register but it is full of duplications. It may not be practicable to eliminate these.
 Multiply the 1881 figures, by the percentage increase in the national population since 1881.
 If you have the GRO data, use Clive Essery's approach. [??]
 Donovan Murrells has devised the following technique, from a full set of GRO data:
For the current last 10 years of available GRO data, calculate the average age at death.
Subtract this figure from the last year of GRO data available.
Count the number of births, less the number of deaths in this period.
This figure will almost give you the total alive.
You need just to factor in for those who have lived past the average age at death, and are consequently still alive. This factor can be derived from ONS population data.
For example
For 19801990, the average age at death is 80.
In the period, 19101990, there have been 5000 births, but 1000 have died in the period.
This leaves 4000 plus another factor for those alive in 1990. In this case, I have decided the factor is 250.
 Rex Leaver takes an even more direct approach:
"The population [of] bearers of a particular surname can be estimated for any date after, say 1966 (100 years after the index began to show age at death). From each cohort of births in the previous 100 years the appropriate deaths can be subtracted year by year until the survivors are identified at the date in question. This total is then the base from which the population in any earlier year is calculated by adding deaths and subtracting births in the relevant interval. (Deaths abroad through emigration, war service and other causes can undermine the precision of these calculations, but they still leave the estimates reasonably accurate."
(Source: Rex Leaver Families on the move Local Historian, May 1990)

