The Total column shows the total number of people in that county or town with this surname.
For example, there were 263 people called ISAAC in Merthyr at the time of the 1881 census.
The Frequency column shows the percentage of people in this county or town
with this surname. For example, a frequency of 303.0303 in Merthyr means that
303.0303% of the people in Merthyr on census day were called ISAAC.
The Index column shows the relative probability of finding someone called ISAAC
in this county or town, compared with the probability of finding them anywhere in Britain as a whole.
An index of 1 means that if you pick someone at random from this county or town, you have exactly the same
probability of picking someone called ISAAC as if you picked at random from the whole of the UK.
Where the index is higher than 1, then you are more likely to find someone called ISAAC here
than if you picked from the UK as a whole, and where it's lower then you are less likely. The actual figure
shows the level of probability - for example, a figure of 2 would indicate that you are twice as likely to find
someone called ISAAC here than in the UK as a whole, and 10 would make it ten times as likely.
The value of 0.26 in Merthyr means that you are 0.26 times as likely to find
someone with the surname of ISAAC in Merthyr than you would be in the whole of the UK.